Al-Bihani v. Obama

United States Court of Appeals
FOR THE DISTRICT OF COLUMBIA CIRCUIT

Filed: August 31, 2010

No. 09-5051

GHALEB NASSAR AL-BIHANI,
APPELLANT

v.

BARACK OBAMA, PRESIDENT OF THE UNITED STATES, ET AL.,
APPELLEES

Appeal from the United States District Court
for the District of Columbia
(No. 1:05-cv-01312)
______

On Petition for Rehearing En Banc
______

BEFORE: Sentelle, Chief Judge, and Ginsburg,
Henderson, Rogers, Tatel, Garland, Brown, Griffith, and
Kavanaugh, Circuit Judges.

ORDER

Appellant=s petition for rehearing en banc and the
response thereto were circulated to the full court, and a vote
was requested. Thereafter, a majority of the judges eligible to
participate did not vote in favor of the petition. Upon
 2
consideration of the foregoing and the brief of amici curiae, it
is

ORDERED that the petition be denied.

FOR THE COURT:
Mark J. Langer, Clerk
BY: /s/
Michael C. McGrail
Deputy Clerk

* A statement by Chief Judge Sentelle and Circuit Judges
Ginsburg, Henderson, Rogers, Tatel, Garland, and Griffith,
concurring in the denial of rehearing en banc, is attached.

* A statement by Circuit Judge Brown, concurring in the
denial of rehearing en banc, is attached.

* A statement by Circuit Judge Kavanaugh, concurring in the
denial of rehearing en banc, is attached.

* A statement by Senior Circuit Judge Williams is attached.
 SENTELLE, Chief Judge, and GINSBURG, HENDERSON,
ROGERS, TATEL, GARLAND, and GRIFFITH, Circuit Judges,
concurring in the denial of rehearing en banc: We decline to
en banc this case to determine the role of international law-of-
war principles in interpreting the AUMF because, as the
various opinions issued in the case indicate, the panel’s
discussion of that question is not necessary to the disposition
of the merits. See Al-Bihani v. Obama, 590 F.3d 866, 871,
873-74 (D.C. Cir. 2010) (panel opinion); id. at 883-85
(Williams, J., concurring in the judgment); Al-Bihani v.
Obama, No. 09-5051, slip op. at 1 (D.C. Cir. Aug. 31, 2010)
(Kavanaugh, J., concurring in the denial of rehearing en
banc); see also Gov’t’s Resp. to Pet. for Reh’g and Reh’g En
Banc at 1-2 (stating that the dispute over the role of the law of
war does not “change[] the outcome”).
 BROWN, Circuit Judge, concurring in the denial of
rehearing en banc: Denial is the fate of most requests for en
banc review, and almost all requests meet that fate quietly
without comment from the court. I would prefer to follow the
usual pattern here. But this, it seems, is no usual case.
Neither the government’s response to the request for
rehearing nor the opinions accompanying the denial can be
described as “usual.” Al-Bihani’s petition requests the court
take the radical step of incorporating all of international law
as judicially enforceable constraints on the President’s war
powers. The government responds ambivalently, adopting the
questionable strategy of conceding Al-Bihani’s point, but
nonetheless urging denial of rehearing. Seven members of
this court now vote to deny the petition, but append a cryptic
statement that exhibits no apparent function other than to
mystify. One judge offers a scholarly exegesis on the
unenforceability of international law norms as limits on the
President’s war-making authority under the AUMF. And last,
another judge contributes a separate opinion that conceives of
a brave new role for judges in wartime: that of supervisors of
the battlefield.

These are unusual developments, indeed, and their
cumulative effect is to muddy the clear holding of Al-Bihani
that international law as a whole does not limit the AUMF’s
grant of war powers. Although we have avoided en banc
review, we have done so through the costly expedient of
making a rather common-place judicial proposition
impenetrably obscure. Clarity in law is a virtue. In the
context of war, that virtue becomes a life-and-death necessity.
But there appears to be a countervailing motivation behind the
court’s resistance to Al-Bihani’s holding: an intuition about
the domestic role of international law, one that moves below
the surface of the briefs and opinions of this en banc petition
process. Hoping to avoid a resolution that leaves all parties in
doubt about international law’s relation to the AUMF, I write
 2
separately to pull the veil back on that intuition and provide as
much clarity as possible.

The Al-Bihani opinion held as “mistaken” the “premise
that the war powers granted by” the AUMF and other statutes
“are limited by the international laws of war.” Al-Bihani v.
Obama, 590 F.3d 866, 871 (D.C. Cir. 2010). This holding
disposed of Al-Bihani’s international law–based claims and
instead hinged the resolution of his case on “the text of
relevant statutes and controlling domestic caselaw.” Id. at
871–72.

Although Al-Bihani’s rehearing petition challenges the
panel opinion on numerous points, it is his challenge to this
holding that has caused consternation. Seven judges have
embraced a peculiar concurrence that strives to make clear
that the holding was not necessary to the disposition of the
case, providing four citations to that effect. But the
concurrence leaves unclear the reason why this
uncontroversial point is relevant. We grant rehearing when a
panel opinion creates a conflict with Supreme Court or circuit
precedent, or when a case presents a question we deem
exceptionally important. See FED. R. APP. P. 35(a). Neither of
these criteria is affected when an opinion’s disposition is
supported by two independently sufficient alternative
holdings.

Perhaps the seven-member concurrence is implying that
the holding at issue is dictum—a position for which Judge
Williams argued explicitly in his separate opinion at the panel
stage, see Al-Bihani, 590 F.3d at 885 (Williams, J.,
concurring). Under this view, the holding would therefore be
incapable of either creating a conflict with prior law or
presenting an important question. But this notion would be
incorrect. It is a longstanding principle that alternative
 3
holdings each possess precedential effect. See United States
v. Title Ins. & Trust Co., 265 U.S 472, 486 (1924) (“[W]here
there are two grounds, upon either of which an appellate court
may rest its decision, and it adopts both, the ruling on neither
is obiter [dictum], but each is the judgment of the court, and
of equal validity with the other.”); see also Woods v.
Interstate Realty Co., 337 U.S. 535, 537 (1949);
Commonwealth of Mass. v. United States, 333 U.S. 611, 623
(1948). Therefore, if the majority of this court believes the
holding at issue would otherwise satisfy one or both of the en
banc rehearing criteria, a grant of rehearing cannot be avoided
by labeling the holding as unnecessary. Nor will future
litigants be able to avoid the holding’s binding authority by
wielding the same label.

Another possible motivation for the concurrence may be
a desire to accommodate both the government’s eager
concession that international law does in fact limit the AUMF
and the government’s argument that its opinion on the matter
is entitled to “substantial deference.”1 Resp. to Petition for
Rehearing, at 6–8 & n.3. But such a motivation would be
illegitimate. Contrary to the government’s claim, its preferred
statutory interpretation warrants no deference from this court.
A “pure question of statutory construction [is] for the courts
to decide,” INS v. Cardoza-Fonseca, 480 U.S. 421, 446
(1987), and doing so—even when a statute concerns foreign
affairs—is “well within the province of the Judiciary,” Repub.
of Austria v. Altmann, 541 U.S. 677, 701 (2004). Of course,
courts are highly deferential when reviewing challenges to
1
Judge Kavanaugh reads this part of the government’s brief
differently than I do, seeing it as a conflicted argument that leaves
doubt over whether the government truly means what it says. See
infra, at 75–77 (Kavanaugh, J., concurring in denial of en banc
rehearing). I agree the government’s brief is conflicted as a general
matter, but on this point I believe its claim to deference is clear.
 4
executive actions taken pursuant to a grant of wide discretion
“to affect a situation in a foreign territory.” United States v.
Curtiss-Wright Export Corp., 299 U.S. 304, 321 (1936). We
will refrain from requiring “narrowly definite standards by
which the President is to be governed” and will not lightly
endeavor to “limit[] or embarrass[] such powers.” Id. at 322.2
However, even when courts consider the Executive’s historic
practice to inform the interpretation of a statute, they are not
imbuing the President with judicial power.

I sense, then, something more significant than a narrow
concern over dictum or deference at work in the seven-
member concurrence. There is in the scholarly community an
intuition that domestic statutes do not stand on their own
authority, but rather rest against the backdrop of international
norms. This intuition has taken many argumentative forms,
some more emphatic than others. For instance, there are those
scholars who believe domestic statutes are merely suggestive
wordings to which courts can and should append international
legal norms, regardless of congressional intent.3 Others are
more shy, imparting to Congress a general intent to legislate
in conformity with international law and therefore reasoning
that all statutes, unless containing a clear statement otherwise,

2
This was, in fact, precisely the sort of deference the government
received in the panel decision.
3
See, e.g., Jeremy Waldron, Foreign Law and the Modern Ius
Gentium, 119 HARV. L. REV. 129, 144 (2005) (proposing courts
resort to norms located in a universal “ius gentium” to treat
“problems that arise in our courts as though they were questions of
legal science”); Jonathan Turley, Dualistic Values in the Age of
International Legisprudence, 44 HASTINGS L.J. 185, 265, 271
(1993) (advocating courts shift “the emphasis away from
determining congressional intent toward upholding international
principles” and “serve a central political function in the developing
transnational arena”).
 5
should be read by courts to incorporate international legal
norms.4 However this intuition is phrased, perhaps the
majority of judges on this court are apprehensive about
unambiguously rejecting it. So, even though the panel
decision foreclosed the idea, the short concurrence may
represent a wish to leave open a possibility—however
slight—that domestic statutes are in fact subordinate to an
overarching international legal order.

If that is their wish, it is a curious one. The idea that
international norms hang over domestic law as a corrective
force to be implemented by courts is not only alien to our
caselaw, but an aggrandizement of the judicial role beyond
the Constitution’s conception of the separation of powers.
See United States v. Yunis, 924 F.2d 1086, 1091 (D.C. Cir.
1991) (“[T]he role of judges . . . is to enforce the Constitution,
laws, and treaties of the United States, not to conform the law
of the land to norms of customary international law.”). That
aggrandizement is clear in the more extreme scholarly
opinions calling for courts to ignore congressional intent in
favor of international norms. And it is only slightly better
disguised in the superficially restrained claims that Congress
intends to conform its actions with global ideals, and that a
clear statement is required if courts are to be prevented from
reading international law into statutory text. Traditional clear
statement rules are justified on the basis of preserving statutes
against possible nullification by a constitutional value,

4
See, e.g., Ingrid Brunk Wuerth, Authorizations for the Use of
Force, International Law, and the Charming Betsy Canon, 46 B.C.
L. REV. 293, 334–36, 357 (2005); Ralph G. Steinhardt, The Role of
International Law as a Canon of Domestic Statutory Construction,
43 VAND. L. REV. 1103, 1112, 1115 (1990) (positing a
“presumption that Congress intends to conform its statutes to
international standards” in the “absence of a clear statement of
repudiation by Congress”).
 6
keeping both Congress and the judiciary within their
constitutional capacities.5 However, a demand that Congress
clearly enunciate the inapplicability of international norms is
not premised on any constitutional value; nothing in the
Constitution compels the domestic incorporation of
international law. Instead, what such a demand protects is a
policy preference, imputing to Congress a general posture
toward international restrictions and erecting the highest
interpretive hurdle to the legitimate prerogative of Congress
to legislate apart from them. This is a restrained search for
legislative “intent” only in the most Orwellian sense—one
that grants judges license to usurp the legislative role and
dictate to Congress what it is supposed to think. Surprisingly,
proponents of this idea actually claim it guards the separation
of powers. See Wuerth, supra, at 349–50. But if that is the
case, then the cure is truly worse than the disease.

I see much of this scholarly idea in Judge Williams’
separate opinion. While purporting to share Judge
Kavanaugh’s concern about using “gauzy notions of
international law to rein in the executive’s conduct of military
operations,” infra, at 7 (opinion of Williams, J.), Judge
Williams offers a hazy but ominous hermeneutics. Its
animating premise is that Boumediene v. Bush, 128 S. Ct.
2229 (2008), used the Suspension Clause to create an opening
through which the Judiciary now—as a constitutional
matter—“monitor[s]” and “supervise[s] the battlefield
conduct of the U.S. military.” Infra, at 7–8 (opinion of
Williams, J.). In executing this supervisory role, the Judiciary
5
See William N. Eskridge, Jr. & Philip P. Frickey, Quasi-
Constitutional Law: Clear Statement Rules as Constitutional
Lawmaking, 45 VAND. L. REV. 593, 599–609 (1992) (discussing
the constitutional concerns behind canons such as the constitutional
avoidance canon, the rule of lenity, and the presumption in favor of
judicial review).
 7
should survey the spectrum of “international discourse,”
picking and choosing those propositions that exhibit—by the
Judiciary’s lights—“serious reasoning,” “consistent[] and
evenhanded[] appli[cation],” and “practical[ity]” to the point
where they are suitable to control the President’s conduct of
war. Id. at 2, 7. Judge Williams states these propositions
matter-of-factly, even blithely, as routine matters of statutory
interpretation. But that nonchalance is only a mask for what
is, at its core, a radical and sweeping claim, one at odds with
our Constitution and caselaw.

The Constitution entrusts the President—not the
Judiciary—with the conduct of war. “The Framers . . . did not
make the judiciary the overseer of our government,”
Youngstown Sheet & Tube Co. v. Sawyer, 343 U.S. 579, 594
(1952) (Frankfurter, J., concurring), so Boumediene cannot be
read—as Judge Williams suggests—to override that basic
notion and hand courts authority to deem international norms
as binding commands on the Commander-in-Chief. Such a
reading would be in tension with the Supreme Court’s
recognition that courts are “hardly . . . competent” in the
realm of foreign affairs, Banco Nacional de Cuba v.
Sabbatino, 376 U.S. 398, 410 (1964), and with the
constitutional principle that prohibits even Congress, let alone
the Judiciary, from “interfer[ing] with the [Executive’s]
command of forces and the conduct of campaigns,” Ex Parte
Milligan, 71 U.S. (4 Wall.) 2, 139 (1866) (Chase, C.J.,
concurring).

Further, Judge Williams’ proposed role for the Judiciary
goes far beyond the role the Supreme Court envisioned in
Hamdi v. Rumsfeld and Boumediene. The Hamdi plurality
forecast a restrained process that “meddles little, if at all, in
the strategy or conduct of war, inquiring only into the
appropriateness of continuing to detain an individual claimed
 8
to have taken up arms against the United States.” 542 U.S.
507, 535 (2004). It seems farfetched that “inquiring only into
the appropriateness” of detention should be freighted with the
awesome power of deciding which international constraints to
enforce against the President. In a similar vein, the Court in
Boumediene was circumspect about crafting any substantive
rules to control the President’s war powers, repeating that it
was not addressing the “content of the law that governs
petitioners’ detention,” leaving it to the political branches first
to engage in a “debate about how best to preserve
Constitutional values while protecting the Nation from
terrorism.” 128 S. Ct. at 2277. Boumediene’s holding
concerned the jurisdiction of U.S. courts over Guantanamo
habeas petitions, and it strains the jurisdictional nature of that
holding to draw from it a substantive judicial power to spin
international discourse into binding domestic law. It is no
wonder then that Judge Williams does not offer any language
from Boumediene to support his theory of an expanded
judicial role in military affairs.

This sprint into judicial immodesty cannot be redeemed
by Judge Williams’ argument that international law parallels
traditional tools of statutory interpretation, and that by turning
to it for substantive meaning courts are only divining the
intent of Congress. I am unaware of any federal judicial
opinion—and Judge Williams cites none—that has ever
before characterized international discourse as a traditional
tool of statutory interpretation on par with legislative history,
usage in other domestic statutes and cases, or dictionary
definitions. The varied process by which international law is
made—through treaty, tribunal decision, and the constant
churn of state practice and opinio juris—shares few, if any, of
the qualities that give the traditional sources of interpretation
their authority. Courts turn to legislative history because it
comes from the mouths of legislators and therefore arguably
 9
sheds light on their intentions and understandings. Courts
examine the usage of terms in other statutes and judicial
decisions because our law is a closed and coherent system that
strives for internal consistency. And courts consult
dictionaries for the same reason most people do: our law, like
the rest of our society, is dependent on language’s technical
meaning among American English speakers. On none of
these grounds can the use of international law be justified.

As Judge Kavanaugh explains in his detailed
concurrence, international norms outside of those explicitly
incorporated into our domestic law by the political branches
are not part of the fabric of the law enforceable by federal
courts after Erie. See infra, at 15–21 (Kavanaugh, J.,
concurring in denial of en banc rehearing). They therefore do
not help courts to determine congressional intent or to
recognize the wider coherence of the law. And international
discourse, unlike a dictionary, is anything but a source of
specific, technical, and shared linguistic meaning. Judge
Williams concedes this point, characterizing international law
as often “vague and deficient,” consisting of “gauzy notions”
that are prone to “misuse” by nations for “political
purpose[s],” and subject to official criticism by our elected
representatives. Infra, at 7 (opinion of Williams, J.). How
can sifting through such an unstable and unreliable trove of
meaning be likened to opening a dictionary? How is it
advisable or legitimate for courts to take on such a
treacherous task, especially when the political branches
possess the competency and traditional duty to do the sifting
themselves by domestically incorporating international law
through statute or rendering treaties self-executing?

But suppose we ignore the questionable propriety of
Judge Williams’ interpretive method and endeavor to apply it
in this case. Ironically—and perhaps paradoxically—we
 10
likely would double-back to the same conclusion that
international law does not limit the AUMF. The phrase in the
AUMF on which Al-Bihani hinges his argument is “necessary
and appropriate,” which he contends modifies the word
“force” by prohibiting conduct not approved by international
law. The closest analogy in domestic law is the phrase
“necessary and proper,” which, as Judge Kavanaugh notes in
his concurrence, has in its constitutional and statutory
provenance been consistently interpreted to broaden rather
than to constrain discretion. See, e.g., Legal Tender Cases, 79
U.S. (12 Wall.) 457, 550 (1870) (“[T]he auxiliary powers,
those necessary and appropriate to the execution of other
powers singly described . . . are grouped in the last clause of
section eight of the first article [the Necessary and Proper
Clause].”) (emphasis added). Turning to international
materials does not yield a different meaning. Usage of the
phrase “necessary and appropriate” on the international plane
grants nations wide discretion to act and does not purport to
constrain them with international law. One example—among
many—is U.N. Security Council Resolution 1624, which in
three separate clauses calls upon states “to take all measures
as may be necessary and appropriate and in accordance with
their obligations under international law” to counter
incitement to terrorist acts. S.C. Res. 1624, ¶¶ 1, 3, U.N. Doc.
S/RES/1624 (Sept. 14, 2005) (emphasis added); see also id.
pmbl. That the Security Council felt the need to append
international law obligations to “necessary and appropriate”—
three times, no less—indicates the phrase does not
automatically incorporate such obligations.

But putting aside the preceding discussion (and the odd
conceptual loop it creates), I reiterate that consulting
international sources in that manner is not something judges
have in their interpretive toolbox. The only generally
applicable role for international law in statutory interpretation
 11
is the modest one afforded by the Charming Betsy canon,
which counsels courts, where fairly possible, to construe
ambiguous statutes so as not to conflict with international law.
See RESTATEMENT (THIRD) OF THE FOREIGN RELATIONS LAW
OF THE UNITED STATES § 114 (1987); see also Sampson v.
Fed. Repub. of Germany, 250 F.3d 1145, 1152 (7th Cir.
2001).6 However, Judge Williams does not appear to confine
international law to such a narrow space. By including
international discourse among the traditional tools available to
courts when interpreting statutes, Judge Williams is not
limiting the application of international law to ambiguous
statutory text. Generally, a statute’s text is only ambiguous
if, after “employing traditional tools of statutory
construction,” a court determines that Congress did not have a
precise intention on the question at issue. Chevron, U.S.A.,
Inc. v. Natural Res. Def. Council, Inc., 467 U.S. 837, 843 n.9
(1984). It is at this point—analogous to Chevron Step Two—
that the Charming Betsy canon has had any application in
federal courts. But Judge Williams implies that international
law should be consulted in the first instance to influence

6
I note the Charming Betsy canon was not invoked in the panel
opinion because it is not applicable to this case. First, the relevant
text of the AUMF is not ambiguous. The phrase “necessary and
appropriate” is broad, but wide breadth is not tantamount to
ambiguity, particularly when a phrase has a stable interpretive
pedigree. Second, even if the phrase were ambiguous, the canon
only applies to statutory interpretations that would violate
international law. An interpretation declining to place international
legal constraints on the President does not, by itself, place the
United States in violation of international law. It merely affirms the
President’s normal prerogative to observe or abrogate international
obligations. Judge Kavanaugh also details other persuasive reasons
why Charming Betsy does not apply in this case. See infra, at
45–66 (Kavanaugh, J., concurring in the denial of en banc
rehearing).
 12
interpretation at the same level as traditional interpretive
tools, making its use predicate to a finding of ambiguity. This
implication has the secondary effect of eviscerating the
limiting principle of the Charming Betsy canon that it only
exerts a negative force on the meaning of statutes, pushing
them away from meanings that would conflict with
international law. Courts do not apply Charming Betsy as an
affirmative indicator of statutory meaning. See, e.g.,
Sampson, 250 F.3d at 1152–53 (holding the Charming Betsy
canon does not require “federal statutes [to be] read to reflect
norms of international law”); Princz v. Fed. Repub. of
Germany, 26 F.3d 1166, 1174 & n.1 (D.C. Cir. 1994)
(rejecting dissent’s argument that statutes must be read
“consistently with international law” and must be presumed to
“incorporate[] standards recognized under international law,”
Princz, 26 F.3d at 1183 (Wald, J., dissenting)). However,
under Judge Williams’ method, I see no reason why courts
would be bound by this rule, since traditional interpretive
sources are normally viewed as indicative of affirmative
meaning. These inconsistencies with the Charming Betsy
canon make clear that Judge Williams’ proposal cannot
possibly be correct. If it were, it would be a mystery why
American jurisprudence would even bother to enunciate an
interpretive canon like the Charming Betsy. Judge Williams’
approach would make that canon vestigial, foolish even—akin
to a canon limiting the use of dictionaries.

Most troubling of all is the grotesque non sequitur that
Congress must have intended to incorporate international law
through the AUMF because it would be odd to think Congress
“embrace[d]” a long history of wartime atrocity, from the
Rape of Nanking to the massacre at Lidice. Judge Williams
may believe that the only barrier that would hold back our
nation from a descent into Nazism is an enlightened judiciary
standing at the precipice, wielding international norms our
 13
polity is presumably unable to muster from within.7 But that
belief cannot change the plain text of the AUMF, its
legislative history, or the longstanding congressional practice
of granting “the President a degree of discretion and freedom
from statutory restriction” necessary to carry out his foreign
affairs duties, Curtiss-Wright, 299 U.S. at 320.

There is no indication that the AUMF placed any
international legal limits on the President’s discretion to
prosecute the war and, in light of the challenge our nation
faced after September 11, 2001, that makes eminent sense.
Confronted with a shadowy, non-traditional foe that
succeeded in bringing a war to our doorstep by asymmetric
means, it was (and still is) unclear how international law
applies in all respects to this new context. The prospect is
very real that some tradeoffs traditionally struck by the laws
of war no longer make sense. That Congress wished the
President to retain the discretion to recalibrate the military’s
strategy and tactics in light of circumstances not contemplated
by our international obligations is therefore sensible, and
reflects the traditional sovereign prerogative to violate
international law or terminate international agreements. See
Garcia-Mir v. Meese, 788 F.2d 1446, 1455 (11th Cir. 1986)
(“[T]he power of the President to disregard international law
in service of domestic needs is reaffirmed.”); RESTATEMENT
(THIRD) OF THE FOREIGN RELATIONS LAW OF THE UNITED
STATES § 339 (describing power of the President to suspend or
terminate international agreements).8

7
Our nation has in fact established workable norms forbidding such
crimes against humanity, as detailed by Judge Kavanaugh. See
infra, at 6–7, 39–45 (Kavanaugh, J., concurring in denial of en banc
rehearing).
8
That courts cannot enforce non–self-executing or non-
incorporated international law against the President does not imply
the United States would escape consequences of breach on the
 14

The only way a court could reach the opposite conclusion
is to go beyond the AUMF’s text, freeing it—as Judge
Williams suggests—to appeal to an international meta-
narrative, one activated whenever a legal issue touches on
matters that strike the judge as transnational in flavor. Judges
act prudently when they consciously forego opportunities for
policymaking. Therefore, ignoring the text and plain meaning
of a statute to privilege a more creative interpretation is the
antithesis of prudence. And, in a time of war, it has the
inconvenient effect of upending more than a century of our
jurisprudence based on an understanding as old as the
Republic: that the “conduct of foreign relations of our
government is committed by the Constitution to the executive
and legislative . . . departments,” not to the judiciary. Oetjen
v. Cent. Leather Co., 246 U.S. 297, 302 (1918).

The only proper judicial role in this case is the truly
modest route taken by the panel opinion in Al-Bihani. We
read “necessary and appropriate” in its traditional sense,
taking Congress at its word that the President is to have wide
discretion. This is a modest course because the President
retains the leeway to implement his authority as broadly or
narrowly as he believes appropriate—consistent with
international law or not—and the legislature, in turn, may add
whatever limits or constraints it deems wise as the war
progresses. This ensures that wartime decisions will be
informed by the expertise of the political branches, stated in a
clear fashion, and that the decisionmakers will be accountable
to the electorate.

international plane. Whether to incur such consequences is part of
the political calculus the President performs when deciding to
disregard international obligations.
 15
None of those benefits accrue if the conduct of the
military is subject to judicial correction based on norms of
international discourse. Such an approach would place
ultimate control of the war in the one branch insulated from
both the battlefield and the ballot box. That would add further
illegitimacy to the unpredictable and ad hoc rules judges
would draw from the primordial stew of treaties, state
practice, tribunal decisions, scholarly opinion, and foreign law
that swirls beyond our borders. It is no comfort to the
military to say, as Judge Williams does, that courts will only
apply international rules they deem to possess the qualities of
serious reason, evenhandedness, and practicality. Those are
not judicially manageable standards. Those are buzzwords,
the pleasing sound of which nearly lulls the mind into missing
the vision of judicial supremacy at the heart of Judge
Williams’ opinion.
 KAVANAUGH, Circuit Judge, concurring in the denial of
rehearing en banc:

In the 2001 Authorization for Use of Military Force,
Congress authorized the President to wage war against al
Qaeda and the Taliban. That war continues. At the
President’s direction, the U.S. military is detaining Al-Bihani
as an enemy belligerent in the ongoing conflict. Al-Bihani
has asked this Court to order his release from U.S. military
custody. He argues that international-law principles prohibit
his continued detention.

The premise of Al-Bihani’s plea for release is that
international-law norms are judicially enforceable limits on
the President’s war-making authority under the AUMF. Even
accepting that premise, Al-Bihani cannot prevail in this case.
As the panel opinion correctly concludes, Al-Bihani’s
arguments misconstrue international law and overlook
controlling federal statutes such as the Military Commissions
Acts of 2006 and 2009.

In any event, as the panel opinion also states, the premise
of Al-Bihani’s argument is incorrect. International-law norms
that have not been incorporated into domestic U.S. law by the
political branches are not judicially enforceable limits on the
President’s authority under the AUMF. This separate opinion
explains at great length my reasons for reaching that
conclusion.

Al-Bihani’s invocation of international law raises two
fundamental questions. First, are international-law norms
automatically part of domestic U.S. law? Second, even if
international-law norms are not automatically part of
domestic U.S. law, does the 2001 AUMF incorporate
international-law principles as judicially enforceable limits on
the President’s wartime authority under the AUMF? The
answer to both questions is no.
 2

First, international-law norms are not domestic U.S. law
in the absence of action by the political branches to codify
those norms. Congress and the President can and often do
incorporate international-law principles into domestic U.S.
law by way of a statute (or executive regulations issued
pursuant to statutory authority) or a self-executing treaty.
When that happens, the relevant international-law principles
become part of the domestic U.S. law that federal courts must
enforce, assuming there is a cognizable cause of action and
the prerequisites for federal jurisdiction are satisfied. But in
light of the Supreme Court’s 1938 decision in Erie Railroad
Co. v. Tompkins, 304 U.S. 64 (1938), which established that
there is no federal general common law, international-law
norms are not enforceable in federal courts unless the political
branches have incorporated the norms into domestic U.S. law.
None of the international-law norms cited by Al-Bihani has
been so incorporated into domestic U.S. law.

Second, the 2001 AUMF does not expressly or impliedly
incorporate judicially enforceable international-law limits on
the President’s direction of the war against al Qaeda and the
Taliban. In authorizing the President to employ force, the
AUMF authorizes the President to command the U.S. military
to kill, capture, and detain the enemy, as Commanders in
Chief traditionally have done in waging wars throughout
American history. Congress enacted the AUMF with
knowledge that the U.S. Constitution and other federal
statutes would limit the President’s conduct of the war. But
neither the AUMF’s text nor contemporaneous statements by
Members of Congress suggest that Congress intended to
impose judicially enforceable international-law limits on the
President’s authority under the AUMF.
 3
Moreover, for three alternative reasons, the Charming
Betsy canon does not authorize courts to employ international-
law norms when interpreting a statute like the AUMF that
broadly authorizes the President to wage war against a foreign
enemy. To begin with, in the post-Erie era, the canon does
not permit courts to alter their interpretation of federal statutes
based on international-law norms that have not been
incorporated into domestic U.S. law. Indeed, since Erie was
decided, the Supreme Court has applied that canon only to
support the presumption that a federal statute does not apply
extraterritorially. Even if one disagrees with that initial
reason for not applying Charming Betsy, however, courts may
not invoke the canon against the Executive. Under basic
principles of administrative law, the Executive generally has
the authority to interpret ambiguous statutes within the
bounds of reasonableness and, in so doing, to weigh
international-law considerations as much or as little as the
Executive sees fit. And even if one also disagrees with that,
there is another, still narrower reason why Charming Betsy
does not apply here: Courts have never applied the Charming
Betsy canon against the Executive to limit the scope of a
congressional authorization of war. For good reason: To the
extent there is ambiguity in a statutory grant to the President
of war-making authority, the President – not an international
tribunal or international law – is to resolve the ambiguity in
the first instance. See Dep’t of the Navy v. Egan, 484 U.S.
518, 530 (1988); cf. Chevron U.S.A. Inc. v. Natural Res. Def.
Council, Inc., 467 U.S. 837, 842-45 (1984).

Al-Bihani relatedly suggests that Hamdi v. Rumsfeld, 542
U.S. 507 (2004), already held that the AUMF incorporates
international-law norms and that courts therefore must
enforce international-law limits against the President. That is
incorrect: Hamdi never stated that the AUMF incorporates
judicially enforceable international-law limits on the
 4
President’s authority, which of course would have been a
momentous and unprecedented holding.

In sum, a federal court lacks legitimate authority to
interfere with the American war effort by ordering the
President to comply with international-law principles that are
not incorporated into statutes, regulations, or self-executing
treaties.

Before proceeding to the analysis of these issues, I
emphasize three overarching points about the position
advanced in this separate opinion.

First, this opinion recognizes and reinforces the
traditional roles of Congress, the President, and the Judiciary
in national-security-related matters – roles enduringly
articulated in Justice Jackson’s separate opinion in
Youngstown Sheet & Tube Co. v. Sawyer, 343 U.S. 579
(1952). Courts enforce constitutionally permissible
constraints imposed by Congress on the President’s war
powers. See Hamdan v. Rumsfeld, 548 U.S. 557 (2006);
Youngstown, 343 U.S. at 634-655 (Jackson, J., concurring);
see generally David J. Barron & Martin S. Lederman, The
Commander in Chief at the Lowest Ebb – Framing the
Problem, Doctrine, and Original Understanding, 121 HARV.
L. REV. 689, 761-66 (2008). So, too, courts enforce judicially
manageable limits imposed by the U.S. Constitution on the
President’s war powers. See Boumediene v. Bush, 128 S. Ct.
2229 (2008); Hamdi, 542 U.S. 507. But courts may not
interfere with the President’s exercise of war powers based on
international-law norms that the political branches have not
seen fit to enact into domestic U.S. law.

Second, the limited authority of the Judiciary to rely on
international law to restrict the American war effort does not
 5
imply that the political branches should ignore or disregard
international-law norms. The principles of the international
laws of war (and of international law more generally) deserve
the respect of the United States. Violating international-law
norms and breaching international obligations may trigger
serious consequences, such as subjecting the United States to
sanctions, undermining U.S. standing in the world
community, or encouraging retaliation against U.S. personnel
abroad. Therefore, Congress and the President are often well-
advised to take account of international-law principles when
considering potential legislation or treaties. And even when
international-law norms have not been incorporated into
domestic U.S. law, the Executive Branch, to the extent
permissible under its constitutional and statutory authority, is
often wise to pay close attention to those norms as a matter of
sound policy, international obligation, or effective foreign
relations. See, e.g., Harold Hongju Koh, Legal Adviser, U.S.
Department of State, The Obama Administration and
International Law: Address at the Annual Meeting of the
American Society of International Law (Mar. 25, 2010); John
B. Bellinger III, Legal Adviser, U.S. Department of State,
Testimony Before the Senate Committee on Foreign Relations
(April 15, 2008), reprinted in part in DIGEST OF UNITED
STATES PRACTICE IN INTERNATIONAL LAW 2008, at 887-88
(Elizabeth R. Wilcox ed.); Letter from Gen. Colin L. Powell
to Sen. John McCain (Sept. 13, 2006), reprinted at 152 CONG.
REC. S10,412 (daily ed. Sept. 28, 2006).

But in our constitutional system of separated powers, it is
for Congress and the President – not the courts – to determine
in the first instance whether and how the United States will
meet its international obligations. When Congress and the
President have chosen not to incorporate international-law
norms into domestic U.S. law, bedrock principles of judicial
 6
restraint and separation of powers counsel that courts respect
that decision.

Third, consistent with that constitutional division of
authority, Congress has enacted a significant body of
legislation to prohibit certain wartime actions by the
Executive and military that contravene American values. For
example, Congress has adopted a detailed and extensive
Uniform Code of Military Justice, which governs many
aspects of military conduct. See 10 U.S.C. §§ 801-946.
Congress also has passed separate laws banning genocide and
war crimes, including laws criminalizing grave breaches of
the Geneva Conventions (such as rape, torture, and murder).
See, e.g., 18 U.S.C. §§ 1091, 2441. In addition, acting
pursuant to congressional authorization, the Executive Branch
has promulgated numerous legally binding rules that regulate
wartime conduct of the military. See, e.g., Enemy Prisoners
of War, Retained Personnel, Civilian Internees and Other
Detainees, Army Reg. 190-8, § 1-1(b) (Oct. 1, 1997). Those
laws, along with many other statutes and regulations, together
constitute a comprehensive body of domestic U.S. laws of
war.

In his thoughtful opinion in connection with the denial of
rehearing, Judge Williams says that it “would be an odd
member of Congress who supposed that in authorizing the use
of military force he was embracing uses equivalent to all such
uses that have ever occurred: think Nanking 1937-38; Katyn
1940; Lidice 1942; My Lai 1968.” Williams Op. at 2-3. I
agree entirely with Judge Williams on that point, but not
because I believe Congress intended for U.S. courts to enforce
international-law norms against the Executive. Rather, when
Congress authorized war in 2001, it did so knowing that
domestic U.S. law already prohibited a variety of improper
wartime conduct. Judge Williams’ worrisome hypotheticals
 7
are thus already taken care of – by the domestic U.S. laws of
war – and do not support his suggestion that the AUMF
incorporates international-law norms. Notably, Judge
Williams points to no examples of violations of international
law that would be contrary to fundamental American values
but that are not already independently prohibited by domestic
U.S. law. There is a good deal of overlap between the
international laws of war and domestic U.S. laws regulating
war. When there is divergence, however, Congress and the
President – not the courts – have the authority in the first
instance to decide whether and how to conform U.S. law to
international law.1

I

Four categories of law are relevant to this case: federal
statutes; self-executing treaties made by the President with the
concurrence of two-thirds of the Senate; non-self-executing
treaties made by the President with the concurrence of two-
thirds of the Senate; and customary international law.2

1
As the opinions concurring in the denial of rehearing en banc
reveal, this question about the relevance of international law to the
AUMF is difficult and intricate. And it is only one of many
complicated issues that the courts have had to grapple with in
conducting habeas proceedings for Guantanamo detainees. In that
regard, it is appropriate here to acknowledge the extraordinary
efforts of the District Judges of this Circuit in expeditiously
addressing and resolving these important and often novel questions.
Even when this Court might disagree with a District Court decision,
that disagreement is with respect and appreciation for the dedicated
work of the District Court on these matters.
2
A self-executing treaty is one that “has automatic domestic
effect as federal law upon ratification.” Medellín v. Texas, 552 U.S.
491, 505 n.2 (2008).
 8

Those four categories do not share the same status in U.S.
law. As I will explain, statutes and self-executing treaties are
domestic U.S. law and thus enforceable in U.S. courts. By
contrast, non-self-executing treaties and customary
international law are not domestic U.S. law. See Medellín v.
Texas, 552 U.S. 491 (2008); Sosa v. Alvarez-Machain, 542
U.S. 692 (2004). Only when international-law principles are
incorporated into a statute or a self-executing treaty do they
become domestic U.S. law enforceable in U.S. courts.

In this case, none of the purported international-law
principles cited by Al-Bihani has been incorporated into a
statute or self-executing treaty. Those principles are therefore
not part of the domestic law of the United States and, on their
own, do not authorize a U.S. court to order Al-Bihani’s
release from U.S. military detention.

A non-self-executing treaty is one that “does not by itself give
rise to domestically enforceable federal law.” The domestic effect
of such a treaty therefore “depends upon implementing legislation
passed by Congress.” Id.
Customary international law is a kind of international common
law; it is a body of rules and principles said to arise informally from
the general and consistent practice of nations. See RESTATEMENT
(THIRD) OF FOREIGN RELATIONS LAW OF THE UNITED STATES
§ 102(2) (1987). Evidence of customary international law includes
judgments and opinions of international tribunals, such as the
International Court of Justice (whose judges are approved by the
U.N. General Assembly and Security Council); judgments and
opinions of other nations’ judicial tribunals; and scholarly writings.
Id. § 103.
 9
A

In our constitutional system, international-law norms may
achieve the status of domestic U.S. law through two
mechanisms: incorporation into a statute (or legally binding
executive regulation adopted pursuant to a statute) or
incorporation into a self-executing treaty.

First, international-law norms may be incorporated into
legislation approved by a majority in both Houses of
Congress and signed by the President (or enacted over a
presidential veto, or by operation of the Constitution’s ten-day
rule). See U.S. CONST. art. I, § 7.

The important role Congress plays in this sphere is
apparent from the text of the Constitution, which specifically
authorizes Congress to “define and punish . . . Offences
against the Law of Nations.” Id. art. I, § 8, cl. 10. The
delegates to the Constitutional Convention expressly assigned
that power to Congress because, as Gouverneur Morris aptly
noted at the Convention, international-law principles are
“often too vague and deficient to be a rule” without
implementing legislation. 2 THE RECORDS OF THE FEDERAL
CONVENTION OF 1787, at 615 (Max Farrand ed., rev. ed.
1937); see also United States v. Smith, 18 U.S. 153, 159
(1820) (international law “cannot, with any accuracy, be said
to be completely ascertained and defined in any public code
recognised by the common consent of nations”).

Consistent with that constitutionally assigned role,
Congress sometimes enacts statutes to codify international-
law norms derived from non-self-executing treaties or
customary international law, or to fulfill international-law
obligations. The Foreign Sovereign Immunities Act of 1976
is a good example of that kind of legislation. The Act
 10
governs federal courts’ jurisdiction to entertain suits against
foreign nations. See 28 U.S.C. §§ 1602-1611. As the
Supreme Court has recognized, “one of the primary purposes
of the FSIA was to codify . . . extant international law.”
Samantar v. Yousuf, 130 S. Ct. 2278, 2289 (2010). Likewise,
the War Crimes Act criminalizes certain conduct – including
torture, rape, and hostage-taking – committed in war by or
against U.S. nationals or members of the U.S. Armed Forces.
The Act provides that this conduct “constitutes a grave breach
of common Article 3” of the 1949 Geneva Conventions. See
18 U.S.C. § 2441(c)(3), (d)(1). Similarly, the Genocide
Convention Implementation Act of 1987 criminalizes
participation in genocide and thereby implements a non-self-
executing treaty to which the United States is a party. See id.
§§ 1091-1093; Convention on the Prevention and Punishment
of the Crime of Genocide, adopted Dec. 9, 1948, S. TREATY
DOC. NO. 81-15; see also Demjanjuk v. Meese, 784 F.2d
1114, 1116 (D.C. Cir. 1986) (Bork, J., in chambers)
(Genocide Convention is not self-executing).

Congress also has passed several laws designed to
implement certain aspects of the international Convention
Against Torture, a non-self-executing treaty to which the
United States is a party. See Convention Against Torture and
Other Cruel, Inhuman or Degrading Treatment or
Punishment, adopted Dec. 10, 1984, S. TREATY DOC. NO.
100-20; Wang v. Ashcroft, 320 F.3d 130, 140 (2d Cir. 2003).
For example, the Torture Victim Protection Act of 1991
creates a civil cause of action to recover damages for torture
committed by foreign officials, “in part to fulfill the
Convention’s mandate that ratifying nations take action to
ensure that torturers are held legally accountable for their
actions.” Price v. Socialist People’s Libyan Arab Jamahiriya,
294 F.3d 82, 92 (D.C. Cir. 2002); see 18 U.S.C. § 1350 note.
Likewise, the federal criminal torture statute establishes
 11
criminal penalties for U.S. nationals (and non-U.S. persons
present in the United States) who commit or conspire to
commit torture outside U.S. territory; that statute fulfills U.S.
obligations under Articles 4 and 5 of the Convention. 18
U.S.C. §§ 2340-2340A; see Renkel v. United States, 456 F.3d
640, 644 (6th Cir. 2006).3

When incorporating international-law norms into
domestic U.S. law, Congress sometimes simply enacts
statutes that refer generically to “international law” (or some
variation thereof) without further defining what international
law requires. For example, federal piracy statutes permit the
capture and forfeiture of vessels used for, and the
imprisonment of individuals who commit, acts of “piracy as
defined by the law of nations.” 18 U.S.C. § 1651; 33 U.S.C.
§§ 384-385; see Ex parte Quirin, 317 U.S. 1, 29 (1942).
Similarly, Congress has authorized the President to use
military force to detain foreign vessels at American ports
when such action is permitted “by the law of nations or the
treaties of the United States.” 22 U.S.C. § 462. It has also
empowered the President to impose sanctions on foreign

3
Relatedly, international-law norms also may be incorporated
into domestic U.S. law by way of executive regulations that have
been adopted pursuant to statutory authorization. For example,
Army Regulation 190-8 governs the treatment of enemy prisoners
of war and other detainees in the custody of the U.S. Armed Forces.
The introduction to that regulation states that it “implements
international law, both customary and codified, relating to” military
detention, including the 1949 Geneva Conventions. Enemy
Prisoners of War, Retained Personnel, Civilian Internees and Other
Detainees, Army Reg. 190-8, § 1-1(b) (Oct. 1, 1997); see 10 U.S.C.
§§ 121, 3061, 6011, 8061 (authorizing issuance of military
regulations). Throughout this opinion, when I refer to domestic
U.S. law, the reference includes statutorily authorized executive
regulations that have the force of law.
 12
countries that use chemical or biological weapons “in
violation of international law.” Id. §§ 5604-5605. In
addition, Article 21 of the Uniform Code of Military Justice
allows military commissions to the extent permitted by statute
or the “law of war.” 10 U.S.C. § 821; see Hamdan v.
Rumsfeld, 548 U.S. 557, 593 (2006) (Congress “preserved
what power, under the Constitution and the common law of
war, the President had had before 1916 to convene military
commissions – with the express condition that the President
and those under his command comply with the law of war”).
Congress likewise has repeatedly directed Executive agencies
to comply with “general” or “generally recognized”
“principles of international law” when administering statutes
that involve activities in international waters. See, e.g., 10
U.S.C. § 113 note (Sunken Military Craft, § 1406(b))
(protection of sunken military vessels); 16 U.S.C. § 1435(a)
(management of national marine sanctuaries); 30 U.S.C.
§ 1421 (issuance of permits for deepwater mining operations);
42 U.S.C. § 9119 (issuance of permits for ocean thermal
energy conversion facilities).

Second, in addition to being incorporated into a statute
(or executive regulation adopted pursuant thereto),
international-law principles may become part of domestic
U.S. law by means of a self-executing treaty that is made by
the President with the concurrence of two-thirds of the Senate.
See U.S. CONST. art. II, § 2, cl. 2; Medellín, 552 U.S. at 505
n.2; Foster v. Neilson, 27 U.S. 253, 314 (1829). A self-
executing treaty is one that “reflect[s] a determination by the
President who negotiated it and the Senate that confirmed it
that the treaty has domestic effect.” Medellín, 552 U.S. at
521. By contrast, a treaty is non-self-executing when it “reads
like a compact between independent nations that depends for
the enforcement of its provisions on the interest and the honor
of the governments which are parties to it.” Id. at 508-09
 13
(quoting Head Money Cases, 112 U.S. 580, 598 (1884))
(internal quotation marks omitted).

Numerous bilateral treaties – agreements between the
United States and one other nation – are self-executing. For
example, the United States has entered into many bilateral
Friendship, Commerce, and Navigation treaties, which define
the civil, property, and commercial rights each treaty country
will afford to nationals of the other. Courts have routinely
held such treaties to be self-executing. See Medellín, 552
U.S. at 521 (“we have held that a number of the ‘Friendship,
Commerce, and Navigation’ Treaties . . . are self-executing”);
Kolovrat v. Oregon, 366 U.S. 187, 191, 196 (1961) (Treaty of
Commerce between United States and Serbia enforceable in
U.S. court); Clark v. Allen, 331 U.S. 503, 508, 517 (1947)
(Treaty of Friendship, Commerce, and Consular Rights
between United States and Germany enforceable in U.S.
court); Asakura v. City of Seattle, 265 U.S. 332, 341 (1924)
(Treaty of Commerce and Navigation between United States
and Japan “operates of itself without the aid of any
legislation” and “will be applied and given authoritative effect
by the courts”); McKesson Corp. v. Islamic Republic of Iran,
539 F.3d 485, 488 (D.C. Cir. 2008) (Treaty of Amity,
Economic Relations, and Consular Rights between United
States and Iran, “like other treaties of its kind, is self-
executing”).

Similarly, bilateral extradition treaties are ordinarily
considered self-executing. See, e.g., Cheung v. United States,
213 F.3d 82, 95 (2d Cir. 2000).

Courts have been somewhat more reluctant to find
multilateral treaties self-executing. See, e.g., Andrea Bianchi,
International Law and U.S. Courts: The Myth of Lohengrin
Revisited, 15 EUR. J. INT’L L. 751, 758 (2004); Curtis A.
 14
Bradley, International Delegations, the Structural
Constitution, and Non-Self-Execution, 55 STAN. L. REV. 1557,
1588 & n.147 (2003). As one court explained, when a
multilateral treaty is ratified by many nations, “some of which
do not recognize treaties as self-executing,” it is difficult for
courts to “ascribe to the language of the treaty any common
intent that the treaty should of its own force operate as the
domestic law of the ratifying nations.” United States v.
Postal, 589 F.2d 862, 878 (5th Cir. 1979).

However, a multilateral treaty still may be self-executing
if its terms indicate that the President and Senate so intended.
An example is the Warsaw Convention, a treaty entered into
by President Franklin Roosevelt with the concurrence of the
U.S. Senate in 1934. It governs the liability of air carriers for
passenger injuries and lost cargo. See Convention for the
Unification of Certain Rules Relating to International
Transportation by Air, opened for signature Oct. 12, 1929, 49
Stat. 3000. The Supreme Court has held that “no domestic
legislation is required to give the [Warsaw] Convention the
force of law in the United States.” Trans World Airlines, Inc.
v. Franklin Mint Corp., 466 U.S. 243, 252 (1984); see, e.g., El
Al Israel Airlines, Ltd. v. Tsui Yuan Tseng, 525 U.S. 155, 176
(1999); Curtin v. United Airlines, Inc., 275 F.3d 88, 90 (D.C.
Cir. 2001). Some other multilateral treaties also have been
regarded as self-executing, such as the Hague Convention on
the Taking of Evidence Abroad in Civil or Commercial
Matters, the General Inter-American Convention for Trade
Mark and Commercial Protection, and the Vienna Convention
on Consular Relations. See Société Nationale Industrielle
Aérospatiale v. U.S. Dist. Ct. for the S. Dist. of Iowa, 482 U.S.
522, 533 (1987); Bacardi Corp. of America v. Domenech, 311
 15
U.S. 150, 161 (1940); Gandara v. Bennett, 528 F.3d 823, 828
(11th Cir. 2008).4

B

By contrast, international-law principles found in non-
self-executing treaties and customary international law, but
not incorporated into statutes or self-executing treaties, are
not part of domestic U.S. law.

The Supreme Court has squarely held that non-self-
executing treaties “are not domestic law.” Medellín, 552 U.S.
at 505 (quotation omitted). Therefore, “responsibility for
transforming an international obligation arising from a non-
self-executing treaty into domestic law falls to Congress.” Id.
at 525-26.

The Supreme Court has likewise indicated that customary
international law is not automatically part of domestic U.S.
law. See Sosa, 542 U.S. 692. Customary international law is
said to arise from the “general and consistent practice of states
followed by them from a sense of legal obligation.”
RESTATEMENT (THIRD) OF FOREIGN RELATIONS LAW OF THE
UNITED STATES § 102(2) (1987). It is a kind of international
common law. It does not result from any of the mechanisms
specified in the U.S. Constitution for the creation of U.S. law.
For that reason, although norms of customary international

4
To say that a treaty is self-executing does not answer the
analytically distinct question whether the treaty confers individually
enforceable rights or a private cause of action. See Medellín, 552
U.S. at 506 n.3. Thus, a treaty may be self-executing in the sense
that it imposes domestic-law obligations on government officials,
yet the treaty itself may not provide a civil cause of action or other
private remedy for violations of those obligations. Id.; see, e.g.,
McKesson, 539 F.3d at 488-89; Gandara, 528 F.3d at 827-29.
 16
law may obligate the United States internationally, they are
not part of domestic U.S. law. Customary-international-law
norms become part of domestic U.S. law only if the norms are
incorporated into a statute or self-executing treaty.

To be sure, there was a time when U.S. courts stated that
customary international law was “part of our law” so that
“where there is no treaty, and no controlling executive or
legislative act or judicial decision, resort must be had to the
customs and usages of civilized nations; and, as evidence of
these, to the works of jurists and commentators.” The
Paquete Habana, 175 U.S. 677, 700 (1900). But that oft-
quoted statement reflected the notion, common in the early
years of the Nation but now discredited, that international law
was part of the general common law that federal courts could
apply. See Sosa, 542 U.S. at 714-15; Erie R.R. Co. v.
Tompkins, 304 U.S. 64, 79 (1938) (historically, the common
law was viewed as “a transcendental body of law outside of
any particular State but obligatory within it unless and until
changed by statute”) (quotation omitted); Curtis A. Bradley &
Jack L. Goldsmith, Customary International Law as Federal
Common Law: A Critique of the Modern Position, 110 HARV.
L. REV. 815, 849 (1997) (the “statement in The Paquete
Habana that CIL [customary international law] was ‘part of
our law’” was “made under the rubric of general common
law” and “did not mean that CIL had the status of federal
law”); Ernest A. Young, Sorting Out the Debate over
Customary International Law, 42 VA. J. INT’L L. 365, 393-94
(2002) (“as virtually all participants in the customary law
debate agree,” before Erie, international law “had the status of
‘general’ law: neither state nor federal”); Bradford R. Clark,
Federal Common Law: A Structural Reinterpretation, 144 U.
PA. L. REV. 1245, 1279-81 & n.169 (1996) (before Erie,
international law, including the laws governing war,
“operated as a set of background rules that courts applied in
 17
the absence of any binding sovereign command to the
contrary”); John F. Manning, Textualism and the Equity of the
Statute, 101 COLUM. L. REV. 1, 99 n.382 (2001) (“Because
courts applying the law of nations believed that they were
merely implementing a pre-existing body of customary law,
this decisionmaking process was not conceived of as
lawmaking per se.”).

But as decided by the Supreme Court in its landmark Erie
decision in 1938, the view that federal courts may ascertain
and enforce international-law norms as part of the general
common law is fundamentally inconsistent with a proper
understanding of the role of the Federal Judiciary in our
constitutional system. In Erie, the Supreme Court famously
held that there is no general common law enforceable by
federal courts. Erie, 304 U.S. at 78. The Court said that “law
in the sense in which courts speak of it today does not exist
without some definite authority behind it.” Id. at 79
(quotation omitted).

Erie means that, in our constitutional system of separated
powers, federal courts may not enforce law that lacks a
domestic sovereign source. Erie “requires federal courts to
identify the sovereign source for every rule of decision,” and
the “appropriate ‘sovereigns’ under the U.S. Constitution are
the federal government and the states.” Bradley &
Goldsmith, Customary International Law, 110 HARV. L. REV.
at 852; see also Anthony J. Bellia Jr., State Courts and the
Making of Federal Common Law, 153 U. PA. L. REV. 825,
891 (2005) (“the rise of positivistic legal thought led courts to
conclude that all law . . . must be attributable to a sovereign
source”); Louise Weinberg, The Curious Notion that the
Rules of Decision Act Blocks Supreme Federal Common Law,
83 NW. U. L. REV. 860, 867 (1989) (“post-Erie positivism has
 18
cleansed American courts of law lacking an identifiable
sovereign source”).5

Some respected scholars have asserted that even though
Erie did away with the idea of federal general common law,
principles of customary international law may still be
recognized as federal common law by federal courts. See,
e.g., Harold Hongju Koh, Is International Law Really State
Law?, 111 HARV. L. REV. 1824, 1835 (1998). But that notion
is very difficult to square with Erie – as other leading scholars
have maintained. Indeed, “[c]ourts and scholars generally
agree that federal common law must be authorized in some
fashion by the Constitution or a federal statute.” Bradley &
Goldsmith, Customary International Law, 110 HARV. L. REV.
at 856; see also Martha A. Field, Sources of Law: The Scope

5
Amici cite several cases in which, they say, “the Supreme
Court has relied upon the laws of war as default rules governing the
conduct of hostilities, applicable absent explicit statutory language
to the contrary.” Br. for Non-Governmental Orgs. & Scholars as
Amici Curiae in Supp. of Reh’g or Reh’g En Banc at 4-5. With one
exception, the cases cited date from the pre-Erie era when
international-law norms were regarded as part of the general
common law discoverable and enforceable by federal courts. Those
cases are not controlling after Erie. Cf. Daniel J. Freeman, The
Canons of War, 117 YALE L.J. 280, 319 (2007) (“[A]s domestic
perception of international law has evolved from being ‘part of our
law’ to a patchwork of ambitious declarations and treaties riddled
with reservations, courts ceased to constrain the breadth of AUMFs
by reference to international law. . . . [A]voidance of international
law – independent of domestic implementation – has not affected
interpretation of an AUMF in a hundred years.”). Only one cited
case – Ex parte Quirin – post-dates Erie. And Quirin supports,
rather than undermines, the framework outlined in this opinion.
That case involved two statutes (Articles of War 12 and 15) that
expressly referenced and thereby incorporated the “law of war.”
See 317 U.S. at 27.
 19
of Federal Common Law, 99 HARV. L. REV. 881, 887 (1986)
(a court “must point to a federal enactment, constitutional or
statutory, that it interprets as authorizing the federal common
law rule”); Henry J. Friendly, In Praise of Erie – and of the
New Federal Common Law, 39 N.Y.U. L. REV. 383, 407
(1964) (federal common law limited to “areas where
Congress, acting within powers granted to it, has manifested,
be it ever so lightly, an intention to that end”).

In light of Erie, it follows that “the wholesale
incorporation of customary international law as federal
common law . . . . offends constitutional norms of federalism,
separation of powers, and democracy,” because such
incorporation would “allow courts to recognize federal norms
that do not derive from any of the lawmaking procedures
specified by the Constitution.” Young, Sorting Out the
Debate, 42 VA. J. INT’L L. at 462.6

In any event, no matter how one might previously have
approached the debate about the post-Erie status of customary
international law, the Supreme Court’s 2004 decision in Sosa
resolved it. See 542 U.S. 692. The Court rejected the notion

6
The Supreme Court has recognized that federal courts retain
authority post-Erie to craft and apply what is sometimes referred to
as “federal common law” in those areas in which courts have
“express congressional authorization to devise a body of law,” as
well as a few “interstitial areas of particular federal interest.” Sosa,
542 U.S. at 726; see also O’Melveny & Myers v. FDIC, 512 U.S.
79, 87 (1994); Boyle v. United Techs. Corp., 487 U.S. 500, 504-06
(1988). For example, Federal Rule of Evidence 501 expressly
authorizes federal courts to recognize evidentiary privileges
according to “the principles of the common law as they may be
interpreted by the courts of the United States in the light of reason
and experience.” See, e.g., Univ. of Penn. v. EEOC, 493 U.S. 182,
188-89 (1990).
 20
that all customary-international-law norms are independently
enforceable in federal court. See id. at 728. The Court
decided that, post-Erie, federal courts could recognize claims
under the Alien Tort Statute for violation of a narrowly
defined subset of international-law norms – not on the theory
that international law is automatically incorporated into U.S.
law, but rather only to give effect to the congressional intent
underlying the ATS’s grant of jurisdiction in 1789. See id. at
724, 729-30, 731 n.19, 732.

Sosa thus confirmed that international-law principles are
not automatically part of domestic U.S. law and that those
principles can enter into domestic U.S. law only through an
affirmative act of the political branches. After all, if
customary international law is automatically federal law, then
the ATS “ought to cover all CIL claims, so long as they also
qualify as torts. But Sosa rejected this view” and instead
“gave domestic legal force to an extremely limited subset of
CIL claims . . . based on its reading of the specific intent of
Congress.” Ernest A. Young, Sosa and the Retail
Incorporation of International Law, 120 HARV. L. REV. F. 28,
29 (2007). The Sosa Court mandated, in other words, “that
any federal common law relating to CIL be grounded in,
conform to, and not exceed the contours of what the political
branches have authorized.” Curtis A. Bradley, Jack L.
Goldsmith & David H. Moore, Sosa, Customary International
Law, and the Continuing Relevance of Erie, 120 HARV. L.
REV. 869, 902 (2007). The Court’s insistence on that point
“simply cannot be reconciled” with the position that “all of
CIL is automatically part of judge-made federal common law
even in the absence of political branch authorization.” Id.
Sosa therefore “would seem to preclude binding the President
to CIL as a matter of domestic law in the absence of an
incorporating statute or treaty.” Id. at 930-31; cf. In re XE
Servs. Alien Tort Litigation, 665 F. Supp. 2d 569, 579 (E.D.
 21
Va. 2009) (“It is clear, then, that Sosa does not incorporate
customary international law . . . into the body of federal
common law in a wholesale manner.”).

C

Al-Bihani cites various international-law norms to
challenge his detention. But Al-Bihani does not invoke any
principles that are actually part of domestic U.S. law
enforceable in U.S. courts. He cites no controlling statutes (or
executive regulations) or self-executing treaties to support his
arguments.

Al-Bihani points to a number of purported international-
law principles: (i) that military detention must terminate at the
conclusion of the specific conflict of capture; (ii) that the
capturing government must either afford a detainee prisoner-
of-war status or have the detainee’s status determined by a
competent tribunal; (iii) that an individual who is not a
member of a nation’s armed forces (including one who takes
up arms as part of a volunteer militia) remains a civilian; (iv)
that military force, including detention, cannot be used against
civilians unless and until they engage in activities constituting
“direct participation in hostilities”; and (v) that a party cannot
become a co-belligerent in a particular international armed
conflict unless the party has notice of the conflict and violates
a duty of neutrality with respect to that conflict.

Based on these and other international-law principles, Al-
Bihani also contends, among other things, that supporters of
al Qaeda or the Taliban cannot be detained unless they engage
in activities constituting “direct participation” in hostilities.

The sources on which Al-Bihani relies for those
international-law arguments fall into two distinct categories.
 22
First, Al-Bihani cites two treaties to which the United States
is a party: the Third and Fourth Geneva Conventions of 1949,
which were made by President Truman in 1949 and concurred
in by the Senate in 1955. These Conventions were
multilateral treaties made in 1949, originally signed by about
60 nations, and later joined by almost all nations. Second, Al-
Bihani cites a variety of other international-law sources: the
1977 Additional Protocols to the Geneva Conventions (which
were signed by the United States under President Carter but
never concurred in by the Senate), commentary from the
International Committee of the Red Cross, and the writings of
various international-law scholars.

None of the sources on which Al-Bihani relies is part of
domestic U.S. law.

Al-Bihani cannot invoke the 1949 Geneva Conventions
as a source of domestic U.S. law enforceable in federal court
for either of two alternative reasons.

To begin with, the 1949 Geneva Conventions are not
self-executing treaties and thus are not domestic U.S. law. To
reiterate, a self-executing treaty is one whose terms “reflect a
determination by the President who negotiated it and the
Senate that confirmed it that the treaty has domestic effect.”
Medellín, 552 U.S. at 521. A treaty is non-self-executing
when it “reads like a compact between independent nations
that depends for the enforcement of its provisions on the
interest and the honor of the governments which are parties to
it.” Id. at 508-09 (quoting Head Money Cases, 112 U.S. at
598) (internal quotation marks omitted).

Under that test, the 1949 Geneva Conventions are non-
self-executing treaties. Common Article 1 of the 1949
Geneva Conventions provides: “The High Contracting Parties
 23
undertake to respect and to ensure respect for the present
Convention in all circumstances.” That language is very
similar to the language found in Article 94 of the United
Nations Charter, which the Supreme Court recently held to be
non-self-executing. Article 94 provides: “Each Member of
the United Nations undertakes to comply with the decision of
the International Court of Justice in any case to which it is a
party.” U.N. Charter art. 94, para. 1 (emphasis added). In
Medellín, the Supreme Court concluded that use of the phrase
“undertakes to comply” – rather than “‘shall’ or ‘must’
comply” – indicated that “further action to give effect to an
ICJ judgment was contemplated” and therefore that the treaty
did not “vest ICJ decisions with immediate legal effect in
domestic courts.” 552 U.S. at 508-09 & n.5. For that reason,
the Medellín Court determined that Article 94 of the U.N.
Charter was non-self-executing.

Under the Medellín analysis, the 1949 Geneva
Conventions’ use of “undertake to respect,” rather than
“shall” or “must” respect, likewise means that “further
action . . . was contemplated” to give the Conventions
domestic effect. Id. at 509 n.5. Like Article 94, therefore, the
1949 Geneva Conventions are not self-executing.

Precedent confirms that the 1949 Geneva Conventions
are non-self-executing. In Johnson v. Eisentrager, 339 U.S.
763 (1950), the Supreme Court analyzed the 1929 version of
the Third Geneva Convention. The Court recognized that
although the Convention granted certain rights to captured
alien enemies in wartime, its “obvious scheme” was that those
rights depended for their enforcement on “political and
military authorities” and that they could be
“vindicated . . . only through protests and intervention of” the
national governments that were parties to the Convention – in
other words, that the 1929 Geneva Convention was non-self-
 24
executing. Id. at 789 n.14; see also Holmes v. Laird, 459 F.2d
1211, 1222 (D.C. Cir. 1972) (Eisentrager found the
“corrective machinery specified in” the 1929 Convention to
be “nonjudicial”).

The Supreme Court’s description of the 1929 Convention
also accurately characterizes the text of the 1949 Geneva
Conventions and supports the conclusion that the 1949
Conventions are non-self-executing. Indeed, our Court
previously ruled as much in an opinion that is not precedential
but is nonetheless persuasive on this point. See Hamdan v.
Rumsfeld, 415 F.3d 33, 39 (D.C. Cir. 2005) (“There are
differences, but none of them renders Eisentrager’s
conclusion about the 1929 Convention inapplicable to the
1949 Convention.”), rev’d on other grounds, 548 U.S. 557
(2006); see also Hamdi v. Rumsfeld, 316 F.3d 450, 468 (4th
Cir. 2003) (“what discussion there is of enforcement [in the
1949 Geneva Conventions] focuses entirely on the vindication
by diplomatic means of treaty rights inhering in sovereign
nations”), vacated and remanded on other grounds, 542 U.S.
507 (2004).

In sum, although the 1949 Geneva Conventions “create[]
an international law obligation on the part of the United
States,” they do not of their “own force constitute binding
federal law.” Cf. Medellín, 552 U.S. at 522. The political
branches may incorporate principles found in the Geneva
Conventions into domestic U.S. law, as they have done on
various occasions. See, e.g., 18 U.S.C. § 2441 (prohibiting
grave breaches of the 1949 Geneva Conventions such as rape,
torture, and murder). So, too, the Executive Branch, acting
within the bounds of its statutory and constitutional authority,
may adhere to the Geneva Conventions as a matter of
international obligation or policy. But because the
 25
Conventions are not self-executing, a court cannot compel
compliance with the Geneva Conventions in this context.

But even assuming arguendo that the 1949 Geneva
Conventions were self-executing as written and ratified,
Congress has since unambiguously repudiated whatever
domestic legal effect the Conventions otherwise might have
had in this habeas setting. Section 5(a) of the Military
Commissions Act of 2006 – a provision that was left intact by
the Military Commissions Act of 2009 – provides in broad
and plain terms: “No person may invoke the Geneva
Conventions or any protocols thereto in any habeas corpus or
other civil action or proceeding to which the United States, or
a current or former officer, employee, member of the Armed
Forces, or other agent of the United States is a party as a
source of rights in any court of the United States.” Pub. L.
No. 109-366, § 5(a), 120 Stat. 2600, 2631. The decision by
the United States to repudiate any judicially enforceable effect
of the 1949 Geneva Conventions in this context resulted from
the considered judgment of two Congresses and two
Presidents – as reflected in the original 2006 Act and in the
2009 determination not to disturb that provision of the 2006
Act.

A statute can repeal a self-executing treaty (or the
domestic force of a self-executing treaty), just as a statute can
repeal a prior statute. See Medellín, 552 U.S. at 509 n.5;
Breard v. Greene, 523 U.S. 371, 376 (1998). Consistent with
that principle, § 5(a) of the 2006 Military Commissions Act
has “superseded whatever domestic effect the Geneva
Conventions may have had in actions such as this.” Noriega
v. Pastrana, 564 F.3d 1290, 1296 (11th Cir. 2009), cert.
denied, 130 S. Ct. 1002 (2010). A habeas court may not
invoke the Geneva Conventions against the Executive. As the
panel opinion in this case concluded, the plain text of the
 26
Military Commissions Act thus precludes Al-Bihani from
relying on the Geneva Conventions in this habeas context.

In a footnote in his rehearing petition, Al-Bihani says that
§ 5(a) of the Military Commissions Act of 2006 “does not
apply to his petition, both as a matter of statutory language
and general retroactivity principles” and that applying it
“would violate the Suspension Clause.” Al-Bihani Pet. for
Reh’g and Reh’g En Banc at 7 n.5. Those arguments have no
merit.

Al-Bihani’s assertion that § 5(a) does not apply to his
petition “as a matter of statutory language” is incorrect. As
already explained, the “statutory language” of § 5(a) plainly
eliminates any domestic effect the Geneva Conventions might
have had in habeas cases, as the Eleventh Circuit correctly
held. See Noriega, 564 F.3d at 1296. In other words, to the
extent the Conventions were once self-executing, “Congress
has effectively unexecuted [them],” at least for habeas matters
of this kind. Curtis A. Bradley, The Military Commissions
Act, Habeas Corpus, and the Geneva Conventions, 101 AM. J.
INT’L L. 322, 341 (2007).

Nor does applying § 5(a) to this dispute pose a
retroactivity problem. The relief Al-Bihani seeks is purely
prospective. He asks that we order his release from military
custody on the ground that his continued, future detention
would be unlawful. “When [an] intervening
statute . . . affects the propriety of prospective relief,
application of the new provision is not retroactive.” Landgraf
v. USI Film Prods., 511 U.S. 244, 273 (1994); see also id. at
293 (Scalia, J., concurring in judgment) (“Since the purpose
of prospective relief is to affect the future rather than remedy
the past, the relevant time for judging its retroactivity is the
very moment at which it is ordered.”). Whether § 5(a) would
 27
apply retroactively to a civil case in which a plaintiff sought
damages for injuries predating enactment of the 2006 MCA is
a question we need not address here.

Al-Bihani’s Suspension Clause argument is likewise
meritless. Section 5(a) does not implicate the Suspension
Clause because it does not suspend the jurisdiction of the
federal courts to hear habeas challenges by detainees such as
Al-Bihani. Rather, by repealing the domestic effect of the
Geneva Conventions in this context, § 5(a) simply addresses
the substantive law that courts may apply to resolve habeas
petitions. See Noriega, 564 F.3d at 1294 (§ 5(a) does not bar
petitioners “from seeking habeas relief,” but merely “changes
one substantive provision of law upon which a party might
rely in seeking habeas relief”); cf. INS v. St. Cyr, 533 U.S. 289
(2001).

Apart from the 1949 Geneva Conventions, Al-Bihani
does not rely on any treaties (either self-executing or non-self-
executing) that have been made by the U.S. President with the
concurrence of two-thirds of the U.S. Senate. The other
international-law sources he cites – the 1977 Additional
Protocols to the Geneva Conventions, Red Cross
commentaries, and writings of international-law scholars –
may reflect or give rise to principles of customary
international law. And those customary-international-law
principles may in turn impose obligations on (or raise policy
considerations for) the United States in its international
relations. The political branches thus may decide to adhere to
those international-law norms. But absent incorporation into
a statute or a self-executing treaty, such customary-
 28
international-law principles are not part of the domestic law
of the United States that is enforceable in federal court.7

* * *

To sum up where we are so far: International-law
principles are not automatically part of domestic U.S. law
enforceable in federal courts. Congress and the President may
incorporate international-law principles into domestic U.S.
law via a statute (or binding executive regulation) or a self-
executing treaty; and when they do so, federal courts will
afford that statute or self-executing treaty the full respect

7
Even if international law were a judicially enforceable
constraint on the President’s authority under the AUMF and even if
international law prohibited detention of mere supporters of al
Qaeda, Al-Bihani’s argument that al Qaeda supporters cannot be
detained would be unavailing. An enemy belligerent may be
detained for the duration of these hostilities. See Hamdi, 542 U.S.
at 518 (plurality opinion of O’Connor, J.) (interpreting scope of
AUMF’s detention authority). And in the Military Commissions
Act of 2006 and the Military Commissions Act of 2009, Congress
provided that the category of enemy belligerents includes those
who “purposefully and materially supported hostilities against the
United States or its coalition partners.” See MCA of 2006 sec.
3(a)(1), § 948a(1)(A)(i), 120 Stat. at 2601; MCA of 2009, Pub. L.
No. 111-84, tit. 18, sec. 1802, § 948a(7)(B), 123 Stat. 2574, 2575
(codified at 10 U.S.C. § 948a(7)(B)). A statute may of course
override pre-existing statutes, including any statutes that
incorporate international law. Therefore, as the panel opinion
explained, the Military Commissions Act definitively establishes
that those who purposefully and materially support al Qaeda may
be detained for the duration of the hostilities, regardless of what
international law might otherwise say about detention of such
supporters. See Al-Bihani v. Obama, 590 F.3d 866, 872 (D.C. Cir.
2010); contra Hamlily v. Obama, 616 F. Supp. 2d 63, 76 (D.D.C.
2009).
 29
ordinarily due to federal statutes. But international-law norms
that are not incorporated into either a statute or a self-
executing treaty – including norms reflected in the 1949
Geneva Conventions and the other international-law sources
relied on by Al-Bihani – do not have the status of domestic
U.S. law enforceable in federal courts.

II

Even though none of the international-law sources Al-
Bihani relies on is part of domestic U.S. law, Al-Bihani and
amici alternatively argue that courts must nonetheless apply
international-law principles in resolving cases under the 2001
Authorization for Use of Military Force, Pub. L. No. 107-40,
115 Stat. 224. In particular, Al-Bihani and amici contend that
we should interpret the AUMF as incorporating international-
law principles that limit the President’s authority under the
AUMF to wage war against al Qaeda and the Taliban.

On its face, this is a radical argument. Al-Bihani and
amici would have the Federal Judiciary limit the scope of the
President’s war-making authority – not based on the
Constitution and not based on express language in a statute or
self-executing treaty, but rather based on international-law
norms that have never been enacted into domestic U.S. law by
American lawmakers.

For the reasons set forth at length below, the argument
advanced by Al-Bihani and amici lacks merit: Congress has
broadly authorized the President to wage war against al Qaeda
and the Taliban. Neither the AUMF’s text nor its legislative
history suggests that Congress intended international-law
principles to limit the scope of that congressional
authorization. Congress often incorporates international-law
principles into federal law; it did not do so here. Courts must
 30
respect that decision. Congress has also enacted a vast body
of domestic U.S. laws of war. But Congress has provided no
indication that it wants courts to freelance and go beyond
Congress’s direction by imposing international-law limits on
the Executive. Moreover, the Charming Betsy canon of
statutory construction does not authorize courts to read
international-law limitations into the authority granted to the
President by the AUMF. The Supreme Court’s decision in
Hamdi v. Rumsfeld, 542 U.S. 507 (2004), similarly does not
support Al-Bihani’s submission.

A

Interpretation of a statute begins (and often ends) with its
text. See Exxon Mobil Corp. v. Allapattah Servs., Inc., 545
U.S. 546, 567-68 (2005); Lamie v. U.S. Trustee, 540 U.S. 526,
534 (2004); Hughes Aircraft Co. v. Jacobson, 525 U.S. 432,
438 (1999).

The text of the 2001 AUMF provides in broad terms:

[T]he President is authorized to use all necessary and
appropriate force against those nations,
organizations, or persons he determines planned,
authorized, committed, or aided the terrorist attacks
that occurred on September 11, 2001, or harbored
such organizations or persons, in order to prevent
any future acts of international terrorism against the
United States by such nations, organizations or
persons.

§ 2(a), 115 Stat. at 224.

The AUMF specifies the enemies against whom the
President is authorized to use force – namely, those nations,
 31
organizations, or persons the President deems to have
sufficient connection to the September 11th attacks.8 The
AUMF affords the President broad discretion with respect to
methods of force, use of military resources, timing, and
choice of targets – except, of course, to the extent the U.S.
Constitution or other federal statutes or self-executing treaties
independently limit the President. In those respects, the
AUMF resembles several prior American war declarations
and authorizations, such as those during World War II. See,
e.g., Joint Resolution of Dec. 8, 1941, ch. 561, 55 Stat. 795
(“the President is hereby authorized and directed to employ
the entire naval and military forces of the United States and
the resources of the Government to carry on war against the
Imperial Government of Japan”); Joint Resolution of Dec. 11,
1941, ch. 564, 55 Stat. 796 (same language, substituting
“Government of Germany”); see also Curtis A. Bradley &
Jack L. Goldsmith, Congressional Authorization and the War
on Terrorism, 118 HARV. L. REV. 2047, 2083 (2005) (the
2001 AUMF “is as broad as authorizations in declared wars
with respect to the resources and methods it authorizes the
President to employ, and with respect to the purposes for
which these resources can be used”).9

8
Under the language of the AUMF, al Qaeda is a permissible
target for the use of military force because President Bush
determined that al Qaeda had planned and committed the
September 11th attacks. Similarly, the Taliban is a permissible
target under the AUMF because President Bush determined that the
Taliban had harbored al Qaeda in Afghanistan.
9
The 2001 AUMF is broader than certain other force
authorizations that have limited the scope of authorized presidential
action by regulating the method of force, controlling the use of
military resources, setting limits on the timing, or dictating or
limiting the choice of targets. For example, in November 1993,
Congress authorized the President to use the U.S. Armed Forces in
Somalia, but only through March 1994 and only for two specific,
 32

There is no indication in the text of the AUMF that
Congress intended to impose judicially enforceable
international-law limits on the President’s war-making
authority under the AUMF. As explained in Part I of this
opinion, Congress has enacted many statutes – including war-
related statutes – that expressly refer to international law. But
unlike those statutes, the AUMF contains no reference to
international law. That omission is critically important here
because, as the Supreme Court has recognized, “Congress
knows how to accord domestic effect to international
obligations when it desires such a result.” Medellín v. Texas,
552 U.S. 491, 522 (2008). Congress did not do so in the
AUMF. So too, in enacting the general War Powers
Resolution, Congress did not require the President to comply
with all facets of international law when commanding and
directing U.S. war efforts. See 50 U.S.C. §§ 1541-1548.10

The silence strongly suggests that Congress did not
intend to impose judicially enforceable international-law

limited purposes – protecting “United States personnel and bases”
and “securing open lines of communication for the free flow of
supplies and relief operations.” Department of Defense
Appropriations Act, 1994, Pub. L. No. 103-139, § 8151(b), 107
Stat. 1418, 1475-77 (1993).
10
Thus, Al-Bihani’s argument that the President’s detention
authority under the AUMF “derives from” international law is
wrong. Al-Bihani Opening Br. at 38. The President’s detention
authority under the AUMF derives from the text of the statute.
Even in the absence of specific congressional authorization,
moreover, the President’s authority to detain at least non-citizen
enemies captured abroad also independently derives from Article II
of the Constitution, as explained below in Part III of this opinion.
 33
constraints on the President’s war-making authority, including
on his detention authority.11

11
Some have suggested that Congress’s use of the phrase “all
necessary and appropriate force” in the AUMF signaled an implicit
intent to bind the President to international-law norms, apparently
on the theory that any act in violation of those norms would not be
“appropriate.” See, e.g., JORDAN J. PAUST, BEYOND THE LAW: THE
BUSH ADMINISTRATION’S UNLAWFUL RESPONSES IN THE “WAR”
ON TERROR 92 (2007); Ingrid Brunk Wuerth, Authorizations for the
Use of Force, International Law, and the Charming Betsy Canon,
46 B.C. L. REV. 293, 325-26 (2005). That interpretation is
fundamentally at odds with how that and similar phrases have been
understood in American law.
For example, the U.S. Constitution endows Congress with
power to “make all Laws which shall be necessary and proper for
carrying into Execution” the “Powers vested by this Constitution in
the Government of the United States.” Art. I, § 8, cl. 18. For
nearly two centuries, the Supreme Court has interpreted the
Necessary and Proper Clause as giving Congress “broad power to
enact laws” that need only be “rationally related to the
implementation of a constitutionally enumerated power.” United
States v. Comstock, 130 S. Ct. 1949, 1956 (2010); see McCulloch v.
Maryland, 17 U.S. 316, 420-21 (1819).
Moreover, in the field of federal administrative law, Congress
has enacted numerous statutes authorizing agency action that is
“necessary and appropriate” to a certain end. See, e.g., 7 U.S.C.
§ 2(a)(1)(E)(i) (CTFC and SEC may issue certain “necessary and
appropriate” rules); 14 U.S.C. § 182(a) (Secretary of Homeland
Security “shall take such action as may be necessary and
appropriate to insure that” the Coast Guard does not discriminate
against women); 16 U.S.C. § 1382(a) (Secretary of Commerce shall
prescribe certain “necessary and appropriate” regulations). Courts
generally have interpreted such language as granting agencies
significant discretion. See, e.g., Turtle Island Restoration Network
v. Nat’l Marine Fisheries Serv., 340 F.3d 969, 976-77 (9th Cir.
2003); Madison-Hughes v. Shalala, 80 F.3d 1121, 1128 (6th Cir.
1996).
 34

Rather, in ascertaining what the AUMF authorizes, courts
presume that Congress authorized the President, except to the
extent otherwise prohibited by the Constitution or statutes, to
take at least those actions that U.S. Presidents historically
have taken in wartime – including killing, capturing, and
detaining the enemy. See Dames & Moore v. Regan, 453 U.S.
654, 686 (1981) (when an Executive practice is “known to
and acquiesced in by Congress” over an extended period,
“Congress may be considered to have consented to the
President’s action”) (quotation omitted); Haig v. Agee, 453
U.S. 280, 293-303 (1981) (finding “congressional
acquiescence” in longstanding Executive practice of
withholding passports for national security reasons); United

In light of this deeply rooted interpretive tradition, the words
“necessary and appropriate” in the AUMF – far from suggesting a
significant limitation on the President’s war powers – are more
naturally read as emphasizing the breadth of the authorization. See
Bradley & Goldsmith, Congressional Authorization, 118 HARV. L.
REV. at 2081 (“It seems unlikely that Congress, which views the
Necessary and Proper Clause expansively, and has the most to gain
from a broad interpretation of the clause, would have used the
phrase ‘necessary and appropriate’ as a way to constrain
presidential authority.”); cf. Bragdon v. Abbott, 524 U.S. 624, 645
(1998) (Congress legislates against the background of how certain
language has previously been interpreted by the other branches of
government); Lorillard v. Pons, 434 U.S. 575, 580-81 (1978)
(same).
In any event, even if there were some reason to think that
Congress intended the words “necessary and appropriate” to
operate as a significant limit on the President’s discretion, there is
zero reason to conclude that Congress intended for international-
law norms to define the term “appropriate.” It is much more
plausible to think that Congress intended to underscore that the
President must operate within the confines of other U.S. laws
passed by Congress. See infra Part II.C.
 35
States v. Midwest Oil Co., 236 U.S. 459, 474 (1915) (“the
long-continued practice [of the President], known to and
acquiesced in by Congress, would raise a presumption . . . of
its consent”); id. at 473 (“in determining the meaning of a
statute . . . weight shall be given to the usage itself”).

B

Even assuming arguendo that the text of the AUMF is
ambiguous on this point – which it is not – the statute’s
legislative history provides no hint that Congress intended to
impose judicially enforceable international-law limitations on
the President’s war-making authority, or on his lesser-
included detention authority. Cf. Allapattah Servs., 545 U.S.
at 568 (legislative history matters at most to the extent it
sheds “a reliable light on the enacting Legislature’s
understanding of otherwise ambiguous terms”). On the
contrary, the House and Senate debates on the AUMF,
although necessarily brief given the urgent timing, contain
numerous statements indicating that Members of Congress
meant to grant the President broad authority in waging a
congressionally approved war. For example:

 “[T]he resolution before us . . . . gives the President
flexibility as Commander in Chief to conduct military
operations as he sees fit.” 147 CONG. REC. 17,116
(2001) (statement of Rep. Hinojosa).

 “[W]e are giving the President the power to conduct a
war.” Id. (statement of Rep. Hunter).

 “[A]s the Commander in Chief, he should and does
have the power to put our American force to the best
use possible across the world.” Id. at 17,129
(statement of Rep. Gekas).
 36

 “Under our Constitution, the President of the United
States is commander in chief. When America is
attacked, he assumes the obligations of the
commander in chief.” Id. at 17,138 (statement of
Rep. Lofgren).

 “The resolution . . . reinforces and supports the
powers granted to the President in the Constitution as
Commander in Chief.” Id. at 17,145 (statement of
Rep. Levin).

 “This resolution gives the President the power to
conduct a war without reporting to or consulting with
Congress.” Id. at 17,151 (statement of Rep. Stark).

 “Let us give our Commander in Chief all necessary
authority to put power behind our purpose . . . .” Id.
at 17,041 (statement of Sen. McCain).

 “The [AUMF] permits the President wide latitude to
use force against the broad range of actors who were
responsible for the September 11 attacks.” Id. at
17,047 (statement of Sen. Biden).

These statements and others like them reinforce the
AUMF’s plain text and do not indicate that Congress intended
to incorporate international-law principles as judicially
enforceable limitations on the President’s wartime authority.12

12
A statement by Representative Clayton of North Carolina
has occasionally been cited as evidence that Congress meant to
impose international-law limits on the President’s authority under
the AUMF. Such reliance is mistaken. Representative Clayton
stated: “The authorization we give the President today is not
 37

In striking contrast to the lack of references to
international law in the congressional debates on the AUMF,
many in Congress did express their intent that the President
act in accordance with the Constitution and extant and future-
enacted U.S. statutes. For example:

 “America is based on a Constitution and our
laws. . . . Nothing in the resolution supersedes any
requirement of the War Powers Act.” Id. at 17,123
(statement of Rep. DeFazio).

 “We must carry out military action within the
parameters of the Constitution and the War Powers
Act, as this resolution provides.” Id. at 17,125
(statement of Rep. Price).

 “I’m not willing to give President Bush carte blanche
authority to fight terrorism. We need to agree to fight
it together within traditional constitutional
boundaries.” Id. at 17,148 (statement of Rep.
Jackson).

unlimited. Congress will monitor progress of our military actions
and work with the President to ensure that our actions under this
resolution are necessary and appropriate, consistent with our values,
in conjunction with our friends and allies, and in accordance with
international laws.” 147 CONG. REC. 17,146. Representative
Clayton’s statement on its face reflects only a desire for Congress
to “work with the President” in the future to ensure compliance
with international law; it did not in any way suggest that the
authority granted in the AUMF was subject to judicially
enforceable international-law limits. And no other statement in the
legislative record suggested that Members of Congress intended the
AUMF to incorporate judicially enforceable international-law
limits.
 38

 “I want those responsible for these heinous crimes to
be hunted down and held accountable – in full
compliance with our Constitution and our laws.” Id.
at 17,150 (statement of Rep. McGovern).

 “This joint resolution is based upon and is an exercise
of the Congress’ constitutional war powers role as
codified in the War Powers Resolution. It also
expressly confirms the conditions on the exercise of
Executive power under that resolution.” Id. at 17,040
(statement of Sen. Levin).

 “[W]e must act within the confines of the
Constitution and the law. I believe that the resolution
before us achieves that goal. . . . When we abide by
our Constitution and our law, we are as strong as we
possibly can be, and we are far stronger than the
malevolent force that we soon will engage.” Id. at
17,041-43 (statement of Sen. Feingold).

The legislative debates preceding passage of the AUMF
show that Congress intended the President to comply with the
Constitution and domestic U.S. law when waging war. But
the debates offer “no suggestion that Congress intended to
impose affirmative CIL [customary international law]
constraints on the President, much less judicially enforceable
CIL constraints.” Curtis A. Bradley, Jack L. Goldsmith &
David H. Moore, Sosa, Customary International Law, and the
Continuing Relevance of Erie, 120 HARV. L. REV. 869, 931
(2007).
 39
C

As was noted in the legislative debates before passage of
the 2001 AUMF, Congress has enacted a considerable amount
of legislation limiting wartime actions by the Executive and
military. This comprehensive set of domestic U.S. laws of
war demonstrates that Congress knows how to control
wartime conduct by the Executive Branch. And it
underscores the illegitimacy of courts’ unilaterally restraining
the Executive’s war effort with additional international-law
restrictions that Congress and the President have not seen fit
to enact into domestic U.S. law.

When Congress passed the AUMF in 2001, it did so
against the background of an expansive body of domestic
U.S. law prohibiting wartime actions by the Executive that
contravene American values. For example, in the War
Crimes Act, Congress criminalized various wartime atrocities
constituting “grave breaches” of Common Article 3 of the
1949 Geneva Conventions. Congress subsequently clarified
that such breaches include murder (defined as killing a person
“taking no active part in the hostilities”), torture, biological
experimentation, mutilation, rape, and hostage-taking. 18
U.S.C. § 2441(c)(3), (d)(1). Another criminal statute
separately prohibits the commission of torture outside of U.S.
territory, including by members of the U.S. military. Id. §
2340A. Likewise, in the Genocide Convention
Implementation Act, Congress criminalized acts of genocide
intended to “destroy, in whole or in substantial part, a
national, ethnic, racial, or religious group.” Id. § 1091(a).

These kinds of laws are not a new phenomenon. Since
early in the Nation’s history, Congress has enacted legislation
governing the conduct of the Executive and the military in
war. In 1800, Congress passed the Articles for the
 40
Government of the Navy, prohibiting (among other things)
murder, theft, plunder, mistreatment of the crew of a captured
vessel, and mistreatment of inhabitants of a port. See Act of
Apr. 23, 1800, ch. 33, § 1, arts. 9, 21, 26-27, 2 Stat. 45, 46,
48. In 1806, Congress enacted the Articles of War to govern
the U.S. Army, prohibiting (among other things) violence
against civilians and malicious destruction of private property.
See Act of Apr. 10, 1806, ch. 20, arts. 32, 54, 2 Stat. 359, 363-
64, 366. In addition, in 1863, Congress passed a statute
expressly enumerating crimes, including murder, rape, and
wounding, that were punishable by court martial when
committed by military personnel in wartime – a prohibition
that was subsequently incorporated into the Articles of War.
Act of Mar. 3, 1863, ch. 75, § 30, 12 Stat. 731, 736; see U.S.
REV. STAT. § 1342, art. 58 (1875).

During the 19th and early 20th Centuries, Congress made
periodic amendments to the Articles of War and the Articles
for the Government of the Navy, and it repeatedly enacted
revised versions of both sets of Articles in their entirety. See
Act of July 17, 1862, ch. 204, § 1, 12 Stat. 600, 600-06
(Articles for the Government of the Navy); U.S. REV. STAT.
§ 1342 (1875) (Articles of War); id. § 1624 (Articles for the
Government of the Navy); U.S. REV. STAT. § 1342 (2d ed.
1878) (Articles of War); id. § 1624 (Articles for the
Government of the Navy); Act of Aug. 29, 1916, ch. 418, § 3,
39 Stat. 619, 650-70 (Articles of War); Act of June 4, 1920,
ch. 227, subch. 2, 41 Stat. 759, 787-812 (Articles of War).
When the United States Code was compiled in 1926, the Code
incorporated both the Articles of War and the Articles for the
Government of the Navy. See 10 U.S.C. §§ 1471-1593
(1926); 34 U.S.C. § 1200 (1926).

In 1950, Congress enacted the Uniform Code of Military
Justice to revise and consolidate the Articles of War and the
 41
Articles for the Government of the Navy (as well as the
disciplinary laws of the Coast Guard). See Act of May 5,
1950, ch. 169, 64 Stat. 107. The UCMJ was substantially
revised in 1968 and again in 1983. See Military Justice Act of
1968, Pub. L. No. 90-632, 82 Stat. 1335; Military Justice Act
of 1983, Pub. L. No. 98-209, 97 Stat. 1393.

The UCMJ sets forth a detailed code of conduct for the
military. Among other things, the UCMJ – like the Articles it
replaced – prohibits members of the U.S. Armed Forces from
committing murder, manslaughter, or rape. 10 U.S.C. §§ 918-
920. Those provisions apply to U.S. soldiers’ conduct in war,
including both conduct directed toward civilians and conduct
directed toward enemy belligerents outside of actual
hostilities. For example, in 1973 the Army Court of Military
Review upheld the court-martial conviction of First
Lieutenant William L. Calley, Jr. under the UCMJ for the
murder of “unarmed, unresisting” Vietnamese villagers at My
Lai. United States v. Calley, 46 C.M.R. 1131, 1165
(A.C.M.R. 1973).

Similarly, the UCMJ prohibits U.S. military personnel
from engaging in “cruelty toward, or oppression or
maltreatment of, any person subject to [their] orders,”
including captured enemy personnel. 10 U.S.C. § 893. The
Court of Appeals for the Armed Forces has held that the
UCMJ imposes on U.S. service members an “affirmative duty
to protect the detainees under [their] charge from abuse,”
which duty is “not affected by” the detainees’ “international
legal status.” United States v. Graner, 69 M.J. 104 (C.A.A.F.
2010) (upholding court-martial conviction under UCMJ for
maltreatment of detainees at military facility in Abu Ghraib,
Iraq); see also United States v. Harman, 68 M.J. 325
(C.A.A.F. 2010) (same); United States v. Smith, 68 M.J. 316
(C.A.A.F. 2010) (same).
 42

The UCMJ also guarantees a number of procedural and
substantive rights to prisoners of war who are accused of
crimes and tried before courts martial. Those rights include
appointment of counsel, equal opportunity to obtain witnesses
and evidence, judicial review, and protection against
compulsory self-incrimination, double jeopardy, and cruel and
unusual punishment. See 10 U.S.C. §§ 802(a)(9), (13), 818,
831, 838, 844, 846, 855, 867-867a, 870.

In addition to those statutes regulating conduct during
war, the War Powers Resolution was enacted by Congress in
1973. In its most pertinent provision, the War Powers
Resolution prohibits the President from deploying U.S.
Armed Forces in hostile situations for more than 62 calendar
days unless Congress specifically authorizes the deployment.
See 50 U.S.C. §§ 1543(a), 1544(b).13

Since passage of the AUMF in 2001, Congress has
enacted additional legislation regulating the Executive’s
conduct of the war. These statutes reveal that Congress has
repeatedly responded with new legislation addressing some of
the unique issues posed by a war against a non-uniformed
enemy. These statutes further demonstrate that Congress
knows how to legislate war-related restrictions on the
Executive – and does not need or intend for the courts to
impose new international-law-based restrictions. For
example, as part of the Detainee Treatment Act of 2005,
Congress provided in broad terms that “[n]o individual in the
custody or under the physical control of the United States
Government, regardless of nationality or physical location,

13
Many Administrations have questioned the constitutionality
of the War Powers Resolution, but that is not relevant for this
discussion.
 43
shall be subject to cruel, inhuman, or degrading treatment or
punishment” and that military detainees in the custody or
control of the Department of Defense shall not be subject to
methods of interrogation not specifically authorized in the
Army Field Manual on Intelligence Interrogation. §§ 1002-
1003, Pub. L. No. 109-148, div. A, tit. 10, 119 Stat. 2739,
2739-40 (codified at 10 U.S.C. § 801 note and 42 U.S.C.
§ 2000dd). And in the Military Commissions Acts of 2006
and 2009, Congress guaranteed unprivileged enemy
belligerents many of the same procedural and substantive
rights the UCMJ affords to prisoners of war. See 10 U.S.C.
§§ 948b(a), 949c(b), 949h, 949j, 949s, 950g, 950h. In the
2006 MCA, Congress also updated the War Crimes Act to
clarify which violations of Common Article 3 of the 1949
Geneva Conventions are punishable as war crimes under
domestic U.S. law. See MCA of 2006, Pub. L. No. 109-366,
sec. 6(b), 120 Stat. 2600, 2633-35 (amending 18 U.S.C.
§ 2441).14
14
The numerous statutory limitations on the wartime actions
of the Executive Branch are supplemented by a variety of legally
binding regulations that the Executive Branch itself has long
promulgated to govern the wartime activities of the U.S. Armed
Forces. In 1863, President Lincoln famously issued General Orders
No. 100, more commonly known as the Lieber Code. See General
Orders No. 100: Instructions for the Government of Armies of the
United States in the Field (Apr. 24, 1863), reprinted in RICHARD
SHELLY HARTIGAN, LIEBER’S CODE AND THE LAW OF WAR 45-71
(1983).
Today, for example, Army Regulation 190-8 governs the
treatment of enemy prisoners of war and other detainees in the
custody of the U.S. Armed Forces. See Enemy Prisoners of War,
Retained Personnel, Civilian Internees and Other Detainees, Army
Reg. 190-8 (Oct. 1, 1997).
When Congress passes a war-authorizing statute like the
AUMF, such regulations – like the statutes described in the text
above – form part of the domestic U.S. law of war background
 44

This extensive body of domestic U.S. laws of war shows
that Congress knows how to impose limits on the wartime
conduct of the Executive Branch when it wants to do so. To
the extent Congress has not seen the need to regulate every
last aspect of the President’s waging of war, we can assume
that Congress has confidence in the President’s ability to
exercise his discretion appropriately – and if it loses such
confidence, Congress may act anew to further limit that
presidential discretion, as it has done on numerous occasions.
See Agee, 453 U.S. at 291-92; cf. Chevron U.S.A. Inc. v.
Natural Res. Def. Council, Inc., 467 U.S. 837, 842-45 (1984).
For present purposes, the critical point is this: The significant
body of laws regulating the Executive undermines any
argument that Congress silently intended for U.S. courts to
impose additional limitations on the Executive’s conduct of a
congressionally authorized war effort. That is especially true
with respect to limitations based on international-law norms
that Congress and the President have chosen not to
incorporate into domestic U.S. law.

This expansive collection of domestic U.S. laws of war
also answers Judge Williams’ concern that it “would be an
odd member of Congress who supposed that in authorizing
the use of military force he was embracing uses equivalent to
all such uses that have ever occurred: think Nanking 1937-38;
Katyn 1940; Lidice 1942; My Lai 1968.” Williams Op. at 2-
3. When a war-related practice is truly subject to universal,
worldwide condemnation to the degree Judge Williams seems

against which Congress legislates. To be sure, the Executive is
always free to change its regulations, but the existence of these
longstanding regulations is not irrelevant when attempting to divine
whether Members of Congress in 2001 actually intended for
international law to operate as an additional judicially enforceable
constraint on the President.
 45
to contemplate, it typically also contravenes American values,
and Congress and the President in turn have tended to ban the
practice. The historical atrocities Judge Williams invokes,
such as rape, torture, and the killing of civilians, are all
prohibited by the domestic U.S. laws described above.
Notably, Judge Williams points to no examples of violations
of international law that are contrary to fundamental
American values but are not already independently prohibited
by domestic U.S. law.

Contrary to Judge Williams’ implication, however, it has
not been Congress’s stated intent or practice to rely on federal
courts to pick and choose additional international-law
principles to constrain the Executive. Judge Williams cites no
evidence to support his view that Members of Congress
actually intended as much when they voted on September 14,
2001.

D

Up to this point, my argument about the AUMF and
international law has been straightforward: Congress knows
how to regulate U.S. war efforts, and it has done so
extensively on many occasions, creating an elaborate body of
domestic U.S. laws of war. And furthermore, Congress
knows how to reference international law when it so chooses.
The AUMF does not reference international law, nor is there
any indication in the legislative debates of a congressional
intent to incorporate international law into the AUMF.
Therefore, we should interpret the AUMF’s textual silence
with respect to international law as indicative of a
congressional intent not to impose judicially enforceable
international-law limits on the President’s war-making
authority. Under this approach, the default presumption is
that international law is not a judicially enforceable limit on a
 46
President’s wartime authority unless Congress expressly says
it is.

Al-Bihani and amici seek to flip that default presumption
by invoking the Charming Betsy canon of statutory
construction. According to their articulation of that canon,
ambiguities in federal statutes must be interpreted in accord
with international-law norms that are not themselves domestic
U.S. law. See Murray v. Schooner Charming Betsy, 6 U.S.
64, 118 (1804); see also RESTATEMENT (THIRD) OF FOREIGN
RELATIONS LAW OF THE UNITED STATES § 114 (1987). Al-
Bihani and amici thus argue that international law is a
judicially enforceable limit on the President’s authority under
a war-authorizing statute unless Congress expressly says it is
not.15

15
When courts construe ambiguous statutes to conform to pre-
existing statutes or self-executing treaties, which are part of
domestic U.S. law, courts are not applying Charming Betsy but
instead are applying a different canon of construction: the familiar
presumption against implied repeal. See Nat’l Ass’n of Home
Builders v. Defenders of Wildlife, 551 U.S. 644, 662-63 (2007) (the
Court “will not infer a statutory repeal” unless Congress’s intention
is clear); Trans World Airlines, Inc. v. Franklin Mint Corp., 466
U.S. 243, 252 (1984) (refusing to find “implicit repeal” of self-
executing treaty in “ambiguous congressional action”).
It is uncontroversial that courts must apply the presumption
against implied repeal when interpreting the AUMF. In Hamdan v.
Rumsfeld, for example, the Supreme Court held that the AUMF did
not impliedly repeal a pre-existing federal statute – Article 21 of the
Uniform Code of Military Justice, 10 U.S.C. § 821 – because
“[r]epeals by implication are not favored.” 548 U.S. 557, 593-95
(2006) (quoting Ex parte Yerger, 75 U.S. 85, 105 (1869)).
But the fact that courts must interpret the AUMF not to
implicitly repeal pre-existing domestic U.S. law obviously does not
mean that courts must interpret the AUMF consistently with
 47

Al-Bihani’s argument is flawed for any of three
alternative reasons discussed below in order from broadest to
narrowest. First, after Erie, Sosa, and Medellín, courts should
not invoke the Charming Betsy canon to conform federal
statutes to non-self-executing treaties or customary
international law. Second, even if the Charming Betsy canon
carries weight in some such cases, it is not properly invoked
against the Executive to conform statutes to non-self-
executing treaties or customary international law. Third, even
if use of the Charming Betsy canon is proper against the
Executive in some cases, it is improper when the statute at
issue is a congressional authorization of war.

1

As an initial matter, Al-Bihani’s invocation of Charming
Betsy fails because he wants courts to alter their interpretation
of the AUMF based on non-self-executing treaties and
customary international law.

After Erie, and particularly after the Supreme Court’s
recent decisions in Sosa and Medellín, there is no legitimate
basis for courts to alter their interpretation of federal statutes
to make those statutes conform with non-self-executing
treaties and customary international law, given that those
sources lack any status as domestic U.S. law.

With respect to non-self-executing treaties, there is a
strong inference that Congress deliberately chose not to
incorporate such treaties into domestic U.S. law. Every non-
self-executing treaty to which the United States is a party has

international-law norms that Congress has not incorporated into
domestic U.S. law.
 48
been presented to and concurred in by the Senate, as required
by the U.S. Constitution. Thus, courts can presume that
Congress is fully aware of the international commitments and
obligations that such treaties embody. The fact that the
Senate has concurred in a non-self-executing treaty – thereby
making it binding on the United States as a matter of
international law and obligation – but Congress has not
passed a statute to implement the treaty domestically,
indicates that Congress did not want those norms to be part of
domestic U.S. law. It therefore makes sense to conclude that
Congress would not want courts to smuggle those norms into
domestic U.S. law through the back door, by using them as a
basis to alter judicial interpretation of a federal statute. See
Medellín, 552 U.S. at 522 (“Congress knows how to accord
domestic effect to international obligations [in a non-self-
executing treaty] when it desires such a result”); Fund for
Animals, Inc. v. Kempthorne, 472 F.3d 872, 880 (D.C. Cir.
2006) (Kavanaugh, J., concurring).

As to customary international law, the problems with
applying Charming Betsy are equally substantial. There was a
good argument for interpreting statutes in light of customary
international law in the days before Erie, when customary-
international-law principles were considered part of the
general common law that all federal courts could enforce.
See, e.g., John F. Manning, Deriving Rules of Statutory
Interpretation from the Constitution, 101 COLUM. L. REV.
1648, 1680 n.146 (2001) (“To the extent that courts applying
the law of nations believed that they were implementing a
preexisting body of customary law, they may have felt
somewhat greater freedom to exercise such independent
common law powers in relation to statutes.”). After Erie and
particularly after Sosa, however, it is clear that customary-
international-law norms, like non-self-executing treaties, are
not part of domestic U.S. law. Congress has incorporated
 49
customary international law into domestic U.S. law on
numerous occasions, including in statutes related to war.
Thus, when Congress does not act to incorporate those norms
into domestic U.S. law, such non-incorporation presumably
reflects a deliberate congressional choice. And it likewise
makes sense to conclude that Congress would not want courts
to smuggle those norms into domestic U.S. law through the
back door by using them to resolve questions of American
law. As the Seventh Circuit has stated, use of the Charming
Betsy canon “so as to effectively incorporate customary
international law into federal statutes when the political
branches of our government may have rejected the
international law at issue seems dubious at best.” Sampson v.
Federal Republic of Germany, 250 F.3d 1145, 1153 (7th Cir.
2001); see also Curtis A. Bradley & Jack L. Goldsmith,
Customary International Law as Federal Common Law: A
Critique of the Modern Position, 110 HARV. L. REV. 815,
871-72 (1997) (affording customary international law its
proper status is arguably inconsistent with the Charming
Betsy canon); Curtis A. Bradley, The Charming Betsy Canon
and Separation of Powers: Rethinking the Interpretive Role of
International Law, 86 GEO. L.J. 479, 536 (1997) (“the
redefinition of federal court power after Erie” “compel[s] re-
examination of” the Charming Betsy canon); Note, The
Charming Betsy Canon, Separation of Powers, and
Customary International Law, 121 HARV. L. REV. 1215,
1221-22 (2008) (“courts arguably violate the separation of
powers when they cabin congressional lawmaking power with
a canon that draws force from a body of law that has no
constitutional origin and does not promote any competing
constitutional value”).16

16
Some maintain that Congress would want a court to alter its
interpretation of a statute based on a non-self-executing treaty or
customary international law. There is no persuasive evidence to
 50

support that romantic view of congressional intent. To begin with,
the best – and only reliable – evidence of congressional intent is
what Congress chooses to enact into domestic U.S. law. Because
Congress regularly acts to incorporate principles derived from non-
self-executing treaties and customary international law into
domestic U.S. law, we can assume that it acts deliberately when it
chooses not to do so.
Moreover, recent decades have seen mounting extra-statutory
evidence that “compliance with international law is often not the
political branches’ paramount concern.” Bradley, The Charming
Betsy Canon, 86 GEO. L.J. at 518. To take one recent example: In
Medellín, the Supreme Court recognized that the United States had
an international-law obligation to comply with the International
Court of Justice’s Avena decision holding that certain U.S.
prisoners, including Medellín, were entitled to review and
reconsideration of their convictions and sentences. See 552 U.S. at
504, 508, 520. But Congress did not act on a bill that would have
implemented the Avena decision domestically, and Medellín was
put to death by the State of Texas. See Medellín v. Texas, 129 S.
Ct. 360, 361 (2008) (per curiam) (possibility that Congress might
implement Avena through domestic legislation was “too remote to
justify” a stay of execution, given that Congress had “not
progressed beyond the bare introduction of a bill”); Jeremy
Lawrence, Treaty Violations, Section 1983, and International Law
Theory, 16 SW. J. INT’L L. 1, 23-24 (2010).
Evidence like this – and there is a good deal of it – makes it
difficult to plausibly maintain that courts vindicate any realistic
notion of actual congressional intent by altering their interpretation
of statutes to conform to non-self-executing treaties or customary
international law. Indeed, if anything, there seems to be evidence
that Congress affirmatively distrusts certain international legal
organizations. For example, in 2004, the House of Representatives
passed a resolution stating that it:
(4) deplores –
(A) the misuse of the International Court of
Justice (ICJ) by a plurality of member nations of the
United Nations General Assembly for the narrow
 51

After Erie, and particularly after Sosa and Medellín,
courts should not invoke the Charming Betsy canon to
conform federal statutes to non-self-executing treaties and
customary international law. Invocation of the Charming
Betsy canon in such circumstances constitutes an “indirect,
‘phantom’ use of international law” that can “have the same
effect as direct incorporation of international law.” Bradley,
The Charming Betsy Canon, 86 GEO. L.J. at 483. Applying
Charming Betsy to customary international law and non-self-
executing treaties would create an “international law-based,
quasi-constitutional ‘penumbra’ that crowds out and inhibits
congressional lawmaking.” Note, The Charming Betsy
Canon, 121 HARV. L. REV. at 1222; cf. Daniel J. Freeman,
The Canons of War, 117 YALE L.J. 280, 321 (2007) (“If the
international law provision is not clearly enforceable – either
through integration in a statute or express self-execution –
then international law yields. However, if international law is
domestically implemented or clearly self-executing, then the
AUMF should not overrule it . . . .”).

political purpose of advancing the Palestinian
position on matters Palestinian authorities have said
should be the subject of negotiations between the
parties; and
(B) the July 9, 2004 advisory judgment of the
ICJ, which seeks to infringe upon Israel’s right to
self-defense, including under Article 51;
(5) regrets the ICJ’s advisory judgment, which is
likely to undermine its reputation and interfere with a
resolution of the Palestinian-Israeli conflict; [and]
(6) commends the President and the Secretary of
State for their leadership in marshaling opposition to the
misuse of the ICJ in this case[.]
H.R. Res. 713, 108th Cong. (2004).
 52
The Supreme Court’s case law since Erie is consistent
with this limited role for international law as a device for
interpreting ambiguous federal statutes. In the seven-plus
decades since the Supreme Court’s landmark 1938 decision in
Erie, the Court has invoked Charming Betsy only
sporadically. It has done so to lend support to a distinct and
far narrower canon of statutory construction: the rule that
absent a clear statement from Congress, federal statutes do not
apply outside the United States. This is often called the
presumption against extraterritoriality. See F. Hoffmann-La
Roche Ltd. v. Empagran S.A., 542 U.S. 155, 164-65 (2004)
(Sherman Act did not apply to foreign effects of price-fixing
conduct); McCulloch v. Sociedad Nacional de Marineros de
Honduras, 372 U.S. 10, 21-22 (1963) (National Labor
Relations Act did not apply to foreign-flag vessel employing
alien seamen); Lauritzen v. Larsen, 345 U.S. 571, 577-78
(1953) (Jones Act did not apply to injuries sustained by alien
seaman aboard foreign-flag vessel in foreign waters).

Those extraterritoriality cases constitute a unique
category. As the Court has recognized, special concerns
counsel against applying domestic U.S. law extraterritorially
because doing so can often conflict with the laws of another
sovereign. In such situations, the presumption against
extraterritoriality serves not just to honor the United States’
international-law obligations as a general matter, but to
“avoid or resolve conflicts between competing laws”
established by two sovereign nations. Lauritzen, 345 U.S. at
582; see also Hoffmann-La Roche, 542 U.S. at 164-65
(presumption “helps the potentially conflicting laws of
different nations work together in harmony”); Sociedad
Nacional, 372 U.S. at 21 (“concurrent application” of U.S.
and foreign law to the same conduct would create a
“possibility of international discord”). The Court’s citation of
Charming Betsy in cases applying the presumption against
 53
extraterritoriality does not support invocation of the canon
outside of that narrow context. Cf. Gov’t Cert. Opp. Br. at
12-13, Koyo Seiko Co. v. United States, 543 U.S. 976 (2004)
(Solicitor General arguing that “cases applying Charming
Betsy have . . . involved avoidance of ‘unreasonable
interference with the sovereign authority of other nations’”)
(quoting Hoffman-La Roche, 542 U.S. at 164).17

In short, neither judicial respect for international law nor
available evidence regarding actual congressional intent nor
post-Erie Supreme Court precedent justifies use of the

17
In Weinberger v. Rossi, 456 U.S. 25 (1982), the Court
considered a statute that prohibited employment discrimination
against U.S. citizens on U.S. military bases overseas unless such
discrimination was permitted by “treaty.” Based on a variety of
considerations including precedent, foreign policy implications, and
legislative history, the Court construed the term “treaty” in the
statute to include congressional-executive agreements with foreign
nations, and thus concluded that the statute did not override a prior
congressional-executive agreement with the Philippines. Id. at 28-
36. The Court also cited Charming Betsy in passing, but the case
did not concern a statute’s interaction with customary international
law or a non-self-executing treaty; rather, it concerned a statute’s
interaction with a congressional-executive agreement, the language
of which made the agreement self-executing and thus domestic U.S.
law. See id. at 26-27 & n.2 (agreement was made pursuant to
statute and provided that the “United States Armed Forces in the
Philippines shall fill the needs for civilian employment by
employing Filipino citizens”) (emphasis added); cf. Medellín, 552
U.S. at 508-09. Therefore, although Weinberger may have
implicated the presumption against implied repeal, it did not
concern the application of the Charming Betsy canon to customary
international law or non-self-executing treaties.
 54
Charming Betsy canon to conform federal statutes to non-self-
executing treaties or customary international law.18

2

Even if one disagrees with that first point about
Charming Betsy, there is an alternative (and far narrower)
reason why the Charming Betsy canon does not apply to
interpretation of the 2001 AUMF: The Charming Betsy canon
may not be invoked against the Executive to conform statutes
to non-self-executing treaties or customary international law.
The basic reason is that the Executive – not international law
or an international tribunal – possesses the authority in the
first instance to interpret ambiguous provisions in statutes and
to determine how best to weigh and accommodate
international-law principles not clearly incorporated into a
statute.

18
To be sure, a U.S. court interpreting a federal statute or
constitutional provision can look at the reasoning of a foreign or
international tribunal on a similar issue. As Justice Ginsburg
recently pointed out, although “foreign decisions do not rank as
precedent” for U.S. courts, “they could be informative in much the
same way as one might gain knowledge or insight from reading a
law review article.” Ruth Bader Ginsburg, “A decent Respect to
the Opinions of [Human]kind”: The Value of a Comparative
Perspective in Constitutional Adjudication, Address to the
International Academy of Comparative Law (July 30, 2010). A
U.S. court examining and giving “respectful attention” to the
reasoning of a non-U.S. tribunal is, of course, entirely different
from a U.S. court either (i) saying that international law is itself
domestic U.S. law or (ii) altering its interpretation of a statute or
constitutional provision so as to conform domestic U.S. law to
international or foreign law.
 55
Since Erie, the Supreme Court has never invoked the
Charming Betsy canon to decide a case against the Executive.
The Ninth Circuit has explained why courts should not do so.
See United States v. Corey, 232 F.3d 1166, 1179 n.9 (9th Cir.
2000).

As Judge Kozinski stated in Corey, a primary purpose of
the Charming Betsy canon is to avoid having a court
“embroil[] the nation in a foreign policy dispute unforeseen
by either the President or Congress.” Id. But when the action
that allegedly violates international law is taken by the
Executive, courts can “presume that the President has
evaluated the foreign policy consequences” of that action
“and determined that it serves the interests of the United
States.” Id.; see also ARC Ecology v. U.S. Dep’t of the Air
Force, 411 F.3d 1092, 1102 (9th Cir. 2005) (same).

Importantly, if courts “construe an authorizing statute
like the AUMF to permit the President to violate international
law,” those courts “would not be placing the United States in
violation of international law. Rather, such a violation would
occur, if at all, only after the Executive Branch, which is both
politically accountable and expert in foreign relations, made
an independent judgment to exercise the authority conferred
by Congress in a way that violated international law.”
Bradley & Goldsmith, Congressional Authorization, 118
HARV. L. REV. at 2098 n.226.

Other judicial decisions have agreed that the Executive’s
interpretation of an ambiguous statute should trump the
Charming Betsy canon and any lurking international-law
norms. For example, the Federal Circuit stated in a
Commerce Department case: “[If] Commerce’s interpretation
of its statutory power falls within the range of permissible
construction . . . that ends our inquiry on this branch of the
 56
case. . . . [E]ven if we were convinced that Commerce’s
interpretation conflicts with the [General Agreement on
Tariffs and Trade], which we are not, the GATT is not
controlling.” Suramerica de Aleaciones Laminadas, C.A. v.
United States, 966 F.2d 660, 667 (Fed. Cir. 1992); see also
Timken Co. v. United States, 354 F.3d 1334, 1343-44 (Fed.
Cir. 2004), cert. denied sub nom. Koyo Seiko Co., 543 U.S.
976.

Scholars have likewise maintained that Charming Betsy
should not trump Chevron or Chevron-like deference with
respect to violations of non-self-executing treaties and
customary international law, given that “[v]iolations of those
forms of law, after all, do not substantially implicate domestic
legal continuity; instead, they implicate foreign relations
issues that would seem to fall within the expertise of the
executive branch.” Curtis A. Bradley, Chevron Deference
and Foreign Affairs, 86 VA. L. REV. 649, 689 (2000); see also
Mary Jane Alves, Reflections on the Current State of Play:
Have U.S. Courts Finally Decided To Stop Using
International Agreements and Reports of International Trade
Panels in Adjudicating International Trade Cases?, 17 TUL. J.
INT’L & COMP. L. 299, 315 (2009) (“an agency’s
interpretation of a silent or ambiguous statute” should not be
rejected under Charming Betsy merely because the agency’s
interpretation conflicts with a non-self-executing treaty);
Kristina Daugirdas, International Delegations and
Administrative Law, 66 MD. L. REV. 707, 748 (2007) (in light
of Chevron, courts applying Charming Betsy in cases
involving the Executive should “read ambiguous statutes to
permit (but not to require) agencies to take actions that are
necessary to comply with international legal obligations”);
Arwel Davies, Connecting or Compartmentalizing the WTO
and United States Legal Systems? The Role of the Charming
Betsy Canon, 10 J. INT’L ECON. L. 117, 143 (2007)
 57
(Charming Betsy should “not be used to vacate agency
interpretations”).

Put another way, Congress has authority in the first
instance to incorporate international-law norms into a statute.
When Congress has not done so, the Executive still has
authority to construe ambiguities in the statute so as not to
violate international-law norms. Absent action by either
Branch to incorporate or abide by international-law norms,
however, by what authority can courts force those norms on
the political branches?

In sum, when Congress has broadly authorized the
President to take certain actions, and that broad authorization
encompasses actions that might in turn violate international
law, courts have no legitimate basis to invoke international
law as a ground for second-guessing the President’s
interpretation.19
19
To the extent some might find the opinions of foreign or
international tribunals helpful in assessing American law, I note as
a point of comparison that the United Kingdom’s Law Lords have
reached the same conclusion with regard to the British equivalent of
the Charming Betsy canon. In a 1991 decision, the Lords ruled that
Britain’s canon of construction requiring courts to interpret statutes
to conform with international law could not be applied to limit
executive action. See R v. Sec’y of State for the Home Dep’t, Ex
parte Brind, [1991] 1 A.C. 696, 748 (H.L.) (opinion of Lord
Bridge) (“where Parliament has conferred on the executive an
administrative discretion without indicating the precise limits
within which it must be exercised, to presume that it must be
exercised within” limits set by international law “would be a
judicial usurpation of the legislative function”); id. at 761-62
(opinion of Lord Acker) (where a statutory grant of authority to the
Secretary of State “contains within its wording no fetter upon the
extent of the discretion it gives,” the Secretary’s failure to comply
with international law does not “render[] his decision unlawful”; a
 58

3

Even if one disagrees with both preceding points about
Charming Betsy, there is another alternative (and still
narrower) reason why the Charming Betsy canon does not
apply to interpretation of the 2001 AUMF. The Charming
Betsy canon may not be invoked against the Executive to limit
the scope of a congressional authorization of war – that is, to
limit a war-authorizing statute to make it conform with non-
self-executing treaties and customary international law.

The Supreme Court has never held that the Charming
Betsy canon applies to a statute that authorizes the President
to use military force against a foreign enemy. For good
reason. Applying Charming Betsy to a statute like the AUMF
would contravene the well-established principle that the
Judiciary should not interfere when the President is executing
national security and foreign relations authority in a manner
consistent with an express congressional authorization (that is,
in Justice Jackson’s Youngstown Category One), at least
unless there is a separate constitutional limitation.

To the extent there is ambiguity in the AUMF, that
ambiguity should be addressed in the first instance by the
President, not by international law or international tribunals.
As Justice Jackson stated in his historic Youngstown opinion,
courts should “indulge the widest latitude of interpretation to
sustain [the President’s] exclusive function to command the
instruments of national force, at least when turned against the
outside world for the security of our society.” Youngstown

contrary conclusion would incorporate international law “into
English domestic law by the back door”).
 59
Sheet & Tube Co. v. Sawyer, 343 U.S. 579, 645 (1952)
(Jackson, J., concurring).

That bedrock tenet of judicial restraint has been
articulated by the Supreme Court in numerous cases. As the
Court stated quite plainly in Department of the Navy v. Egan,
for example, “unless Congress specifically has provided
otherwise, courts traditionally have been reluctant to intrude
upon the authority of the Executive in military and national
security affairs.” 484 U.S. 518, 530 (1988); see also Dames
& Moore, 453 U.S. at 678 (“failure of Congress specifically
to delegate authority does not, ‘especially . . . in the areas of
foreign policy and national security,’ imply ‘congressional
disapproval’ of action taken by the Executive”) (quotation
omitted); Agee, 453 U.S. at 291 (“in the areas of foreign
policy and national security . . . congressional silence is not to
be equated with congressional disapproval”); United States v.
Curtiss-Wright Export Corp., 299 U.S. 304, 322 (1936)
(courts should “hesitate long before limiting or embarrassing”
the President’s exercise of foreign relations authority pursuant
to a congressional authorizing statute) (quotation and
emphasis omitted); cf. Chevron, 467 U.S. at 842-45.20

20
Courts sometimes construe the scope of congressional
authorization more narrowly with respect to war-related activities
against U.S. citizens, in part because of the constitutional avoidance
canon. See Ex parte Endo, 323 U.S. 283, 300 (1944) (“In
interpreting a wartime measure we must assume . . . . that the law
makers intended to place no greater restraint on the citizen than was
clearly and unmistakably indicated by the language they used.”).
But see Hamdi, 542 U.S. at 547 (Souter, J., concurring in part,
dissenting in part, and concurring in judgment) (arguing that
plurality had failed to construe AUMF narrowly with regard to an
American citizen detainee); id. at 574 (Scalia, J., dissenting)
(same).
 60
That deeply rooted tradition of judicial restraint when the
President is executing national security or foreign affairs
statutes pursuant to a broad congressional authorization stems
from at least three interpretive sources – one based on basic
tenets of statutory interpretation and the tripartite separation
of powers; one based on Article II of the Constitution and the
constitutional avoidance canon; and one based on prudential
considerations.

First, as to statutory interpretation, the Supreme Court
has recognized that Congress, for reasons of practical
necessity and efficiency, often assigns broad authority to the
Executive in the areas of national security and foreign policy.
As the Court has noted, the field of national security and
foreign affairs presents “important, complicated, delicate and
manifold problems.” Curtiss-Wright, 299 U.S. at 319. And
“Congress cannot anticipate and legislate with regard to every
possible action the President may find it necessary to take or
every possible situation in which he might act.” Dames &
Moore, 453 U.S. at 678. Moreover, the President, “not
Congress, has the better opportunity of knowing the
conditions which prevail in foreign countries, and especially
is this true in time of war.” Curtiss-Wright, 299 U.S. at 320.
Therefore, “Congress – in giving the Executive authority over
matters of foreign affairs – must of necessity paint with a
brush broader than that it customarily wields in domestic
areas.” Agee, 453 U.S. at 292 (quotation and emphasis
omitted); see also Curtiss-Wright, 299 U.S. at 320 (foreign
affairs statutes “must often accord to the President a degree of
discretion and freedom from statutory restriction which would
not be admissible were domestic affairs alone involved”); cf.
Egan, 484 U.S. at 529 (“protection of classified information
must be committed to the broad discretion of the agency
responsible” because “an outside non-expert body” is not
competent to make or evaluate such judgments).
 61

Courts are thus rightly hesitant to construe foreign affairs
statutes more narrowly than the text indicates, lest they
inadvertently contravene Congress’s prudent and reasonable
decision to afford the President broad discretion in sensitive
and difficult-to-predict national security issues. Put simply,
Congress knows how to limit the Executive’s authority in
national security and foreign policy; there is no reason or
basis for courts to strain to do so absent such congressional
direction.

Second, this traditional deference in interpreting national
security statutes also finds support in the constitutional
avoidance canon. In the domain of foreign relations and
military affairs, the President possesses at least some Article
II authority to act even without congressional authorization,
as explained more fully in Part III below. See, e.g., Egan, 484
U.S. at 529-30; Curtiss-Wright, 299 U.S. at 320. Indeed, in
the text of the AUMF itself, Congress acknowledged that the
President has independent constitutional authority to act
without congressional authorization in defense of the Nation.
See AUMF pmbl., 115 Stat. at 224 (“the President has
authority under the Constitution to take action to deter and
prevent acts of international terrorism against the United
States”); see also War Powers Resolution § 2(c), 50 U.S.C.
§ 1541(c) (President as Commander in Chief has
“constitutional power[]” to introduce U.S. Armed Forces into
hostilities without congressional authorization in response to
an “attack upon the United States, its territories or
possessions, or its armed forces”). That point is perhaps best
exemplified in recent history by a number of significant
military actions taken by President Clinton without
congressional authorization, such as his bombing of suspected
al Qaeda targets in Afghanistan and Sudan in 1998.
 62
Courts are therefore properly reluctant to construe broad
national security statutes like the AUMF more restrictively
than their statutory text, lest the courts interfere with the
President’s independent constitutional authority or have to
confront difficult constitutional questions regarding the scope
of the President’s Article II authority to act without
congressional authorization. See Cass R. Sunstein,
Administrative Law Goes to War, 118 HARV. L. REV. 2663,
2670-71 (2005) (“statutory enactments involving core
executive authority” – such as the “authority to protect the
nation when its security is threatened” – “should be construed
hospitably to the President so as to avoid the constitutional
difficulties that a narrow construction would introduce”); see
also Bradley & Goldsmith, Congressional Authorization, 118
HARV. L. REV. at 2098 (questioning whether the Charming
Betsy canon should apply to “a grant of discretionary
enforcement authority to the President” that “overlaps with
the President’s independent constitutional powers”); WILLIAM
N. ESKRIDGE, JR., DYNAMIC STATUTORY INTERPRETATION
325 (1994) (describing “[s]uper-strong rule against
congressional interference with the president’s authority over
foreign affairs and national security”).

Third, prudential considerations likewise suggest that
Charming Betsy is inapposite when courts interpret war-
authorizing statutes. Construing the AUMF to create
judicially enforceable international-law constraints on the
President’s war-related authority would require the Judiciary
to make highly subjective policy judgments that it is not well-
suited to make – and should not make absent congressional
direction. The President’s execution of foreign affairs statutes
often “requires judgments of policy and principle, and the
foreign policy expertise of the executive places it” – not
courts – “in the best position to make those judgments.” Eric
A. Posner & Cass R. Sunstein, Chevronizing Foreign
 63
Relations Law, 116 YALE L.J. 1170, 1176 (2007); see id. at
1205-07.

Many international-law norms are vague, contested, or
still evolving. Simply determining the precise content of
those norms at any given time entails a considerable exercise
of subjective judgment. Applying them to particular factual
situations adds another layer of subjectivity. See Sosa v.
Alvarez-Machain, 542 U.S. 692, 726 (2004) (“a judge
deciding in reliance on an international norm will find a
substantial element of discretionary judgment in the
decision”); JACK L. GOLDSMITH & ERIC A. POSNER, THE
LIMITS OF INTERNATIONAL LAW 23-24 (2005) (discussing
difficulties in ascertaining content of customary international
law). And deciding how those international-law norms
should apply to a war that differs in fundamental ways from
traditional models of armed conflict presents especially
thorny questions of policy and prudence. Moreover, judicial
assessment of contested international-law norms can take
years, but the President often needs to make military decisions
immediately or at least quickly – a reality that calls for
judicial caution before restraining the President’s exercise of
war powers.

Thus, it is hard to conceive of a task less appropriate for
U.S. judges – or less consistent with our constitutional
structure – than judicial invocation, without a constitutional or
congressional mandate, of uncertain and changing
international-law norms to restrain the President and the U.S.
military in waging a congressionally authorized war abroad.
It is the President’s duty and responsibility to win the war, in
a manner consistent with the Constitution and with
constitutionally permissible limits imposed by Congress.
Courts should not interfere with that effort unless the
 64
Constitution, a federal statute, or a self-executing treaty so
requires.21

21
A fine illustration of the difficulty of applying international-
law norms is the recent back-and-forth over the proper legal
framework for targeted killing of alleged terrorists by the United
States using unmanned aerial vehicles, or “drones,” in Pakistan and
elsewhere.
In March 2010, the Legal Adviser to the U.S. State
Department asserted that U.S. drone operations “comply with all
applicable law, including the laws of war.” Harold Hongju Koh,
Legal Adviser, U.S. Dep’t of State, The Obama Administration and
International Law: Address at the Annual Meeting of the American
Society of International Law (Mar. 25, 2010). The Legal Adviser
took the position that “as a matter of international law, the United
States is in an armed conflict with al-Qaeda, as well as the Taliban
and associated forces” and that “individuals who are part of such an
armed group are belligerents and, therefore, lawful targets under
international law.” Id.
Some of those conclusions were subsequently challenged,
however, by the United Nations Special Rapporteur on
Extrajudicial, Summary or Arbitrary Executions, Professor Philip
Alston. See U.N. Human Rights Council, Report of the Special
Rapporteur on Extrajudicial, Summary or Arbitrary Executions,
Addendum: Study on Targeted Killings, U.N. Doc.
A/HRC/14/24/Add.6 (May 28, 2010) (prepared by Philip Alston).
Special Rapporteur Alston stated that it was “problematic” for the
United States to claim that it is in an armed conflict with al Qaeda,
the Taliban, and associated forces “outside the context of the armed
conflicts in Afghanistan or Iraq,” and that if the United States is not
in an armed conflict with al Qaeda, such targeted killings “cannot
be legal” under international law. Id. ¶¶ 33, 53. Special
Rapporteur Alston also maintained that even assuming the United
States is in an armed conflict with al Qaeda, international law still
would not permit the United States to target individuals based on
mere “membership” in al Qaeda, but would instead require the
United States to demonstrate that those individuals’ conduct rose to
the level of “direct participation in hostilities.” See id. ¶ 58, 62-67.
 65

Consider some of the radical implications of the position
advanced by Al-Bihani and amici. The 15 judges on the
International Court of Justice include judges from China,
Russia, Jordan, Somalia, France, Brazil, and Sierra Leone,
among other nations. Suppose, for example, that the ICJ
issues an important ruling on a matter of international law
related to the U.S. war against al Qaeda. One can have the
greatest respect (as I do) for the judges on the ICJ and at the
same time think it odd for a U.S. court to give more weight to
the views of Chinese and Russian jurists, for example, than to
the interpretation of the U.S. President when the court is
interpreting a domestic U.S. war-authorizing statute that does
not itself reference international law. Yet that is the necessary
and highly irregular result of the approach advocated by Al-
Bihani and his amici.

In light of those statutory, constitutional, and prudential
considerations, we would upend Supreme Court precedent
and basic elements of our constitutional architecture were we
to apply the Charming Betsy canon to war-authorization
statutes such as the 2001 AUMF. Courts should not rely on
Charming Betsy to transform affirmative congressional
authorization of a war into a legislative mandate for courts to
restrain the President’s conduct of that war based on
sometimes vague, contested, or still-evolving international-
law principles.

This rather stark difference of opinion between the U.S. State
Department and the U.N. Special Rapporteur simply underscores
the murkiness and uncertainty surrounding the application of
international-law norms to the war in which the United States is
presently engaged. It suggests that judges should not wade into
debates of this kind and hamper the President’s direction of a war
without a constitutional or congressional mandate to do so.
 66
* * *

To sum up on Charming Betsy: The canon exists to the
extent it supports applying the presumption against
extraterritorial application of federal statutes. Beyond that,
after Erie and particularly after Sosa and Medellín, it is not
appropriate for courts to use the Charming Betsy canon to
alter interpretation of federal statutes to conform them to
norms found in non-self-executing treaties and customary
international law, which Congress has not chosen to
incorporate into domestic U.S. law. In the alternative, even if
one disagrees with that broader proposition and concludes that
use of the Charming Betsy canon is appropriate in some such
cases, it should not be invoked against the Executive Branch,
which has the authority to weigh international-law
considerations when interpreting the scope of ambiguous
statutes. And even if one also disagrees with that, it is not
appropriate for courts to narrow a congressional authorization
of war based on international-law norms that are not part of
domestic U.S. law.

E

Al-Bihani and amici cite Hamdi v. Rumsfeld to support
their argument that the President’s authority under the AUMF
is limited by international law. They assert that Hamdi in
effect already applied Charming Betsy to the AUMF. That
contention is erroneous.

The detainee in Hamdi was a U.S. citizen who argued
that his detention was forbidden by the Non-Detention Act.
That Act prohibits detention of U.S. citizens unless authorized
by statute. See 18 U.S.C. § 4001(a). The relevant questions
for the Hamdi Court, therefore, were (i) whether the AUMF
authorized detention of enemy combatants in the war against
 67
al Qaeda and the Taliban, (ii) whether that authority
encompassed detention of U.S. citizen enemy combatants, and
(iii) whether such detention could last for the duration of the
war, even though the war might last for decades.

Justice O’Connor’s plurality opinion first answered the
threshold question whether the AUMF authorized detention.
It pointed out that detention is a “fundamental incident of
waging war” and, for that reason, is “clearly and
unmistakably authorized” by the AUMF’s grant of authority
to employ “necessary and appropriate” military force. 542
U.S. at 519 (plurality opinion of O’Connor, J.). That point
was, of course, fairly obvious: At its core, war consists of
killing, capturing, and detaining the enemy. In any event, in
reaching that conclusion, the plurality “looked to prior
Executive Branch practice during wartime to inform its
interpretation” of the AUMF. Bradley & Goldsmith,
Congressional Authorization, 118 HARV. L. REV. at 2085.
The plurality also pointed to some international law-of-war
sources as evidence that the “universal agreement and
practice” among civilized nations supported the conclusion
that detention was a fundamental incident of warfare. Hamdi,
542 U.S. at 518 (plurality opinion of O’Connor, J.) (quoting
Ex parte Quirin, 317 U.S. 1, 30 (1942)).

Next, the Court found that the AUMF’s authorization of
detention encompassed detention of enemy combatants who
were U.S. citizens. The Court noted that the United States
had detained U.S. citizens as enemy combatants in the past,
including during World War II. The Court also recognized
that “such a citizen, if released, would pose the same threat of
returning to the front during the ongoing conflict” as a non-
citizen detainee. Id. at 519.
 68
Finally, the Court addressed Hamdi’s concern about
“indefinite or perpetual detention” in light of the expected
duration of the war against al Qaeda and the Taliban. Id. at
521. Hamdi in essence argued that there must be some
implied limit to the duration of the President’s authority under
the AUMF, lest Hamdi spend the rest of his life in detention.
In rejecting that contention, the plurality opinion initially
noted that indefinite detention simply “for the purpose of
interrogation” was not authorized by the AUMF; in other
words, the Court stated the uncontroversial proposition that
detention under the AUMF must be linked to the ongoing
war. Id. More to the point, the plurality opinion stated:
“[W]e understand Congress’ grant of authority for the use of
‘necessary and appropriate force’ to include the authority to
detain for the duration of the relevant conflict, and our
understanding is based on longstanding law-of-war
principles.” Id. By this statement, the plurality rebuffed
Hamdi’s duration-based argument and ruled that the President
could detain Hamdi for the duration of the hostilities, even if
the hostilities lasted for the rest of Hamdi’s life. Insofar as
the “duration of the relevant conflict” language in Justice
O’Connor’s opinion implicitly suggested a limitation on the
President’s detention authority under the AUMF, that
limitation was of course commonsensical: A congressional
authorization for the use of force obviously pertains to the war
for which force is authorized and applies until Congress or the
Commander in Chief ends the war.22

22
In Hamdi, the Court separately held that a U.S. citizen
detainee was entitled under the U.S. Constitution’s Due Process
Clause to a meaningful hearing before a neutral decisionmaker. See
542 U.S. at 509 (plurality opinion of O’Connor, J.); id. at 553
(Souter, J., concurring in part, dissenting in part, and concurring in
judgment). That aspect of Hamdi exemplifies a point made
repeatedly in this opinion: Courts enforce judicially manageable
limits imposed by the U.S. Constitution on the President’s war
 69

The question here is how to interpret Hamdi’s isolated
references to international law. They can be read in one of
two basic ways. On the one hand, they can be read more
narrowly as a direct response to Hamdi’s argument that the
AUMF did not authorize detention, and especially not
indefinite or perpetual detention. A simple response to
Hamdi’s contention was that the AUMF authorizes the
President to employ, at a minimum, those tools and methods
that are traditional and “fundamental incident[s] of waging
war,” and the international laws of war may be one potential
indication that a longstanding Executive practice falls within
that category. As a practical matter, it would be quite odd to
think that Congress, when passing the AUMF, did not intend
to authorize at least what the international laws of war permit,
subject of course to separate prohibitions found in domestic
U.S. law. In that sense, international law can be said to
inform judicial interpretation of the AUMF.

On the other hand, Hamdi is read far more broadly by Al-
Bihani and amici to mean that international law conclusively
defines the limits of the President’s war powers under the
AUMF. On this view, the authority granted to the President
by the AUMF is coextensive with the international laws of
war.

Hamdi should not be read so broadly. Justice
O’Connor’s plurality opinion in Hamdi carefully avoided
stating that any action contrary to international-law norms
would not be authorized under the AUMF. Nowhere did the
Court say something like: “The limits of the President’s
authority under the AUMF are defined by the limits of

powers. See also Boumediene v. Bush, 128 S. Ct. 2229, 2262
(2008).
 70
international law.” Nowhere did the Court say anything such
as: “To the extent the AUMF is ambiguous, we interpret that
ambiguity consistently with international law.” Nowhere did
the Court cite Charming Betsy. Nowhere did the Court
consider the principles of interpretation it has traditionally
applied in national security cases such as Egan, Haig v. Agee,
Dames & Moore, Youngstown, and Curtiss-Wright. One
would expect to find careful analysis of those principles in the
Hamdi opinion if Al-Bihani’s broader reading were correct.
Here, as elsewhere, the dog that didn’t bark is telling.23

To be sure, there is some ambiguity in Hamdi, which
makes it difficult to know for sure what the plurality meant.
As others have noted, the Hamdi plurality “did not explain
how or why [the international laws of war] were relevant.”
Bradley & Goldsmith, Congressional Authorization, 118
HARV. L. REV. at 2088. But there is good reason to adopt the
narrower rather than the broader interpretation. It would have
been momentous and historic for the Court to have held that
the President’s authority under the AUMF is coextensive with

23
I do not agree, therefore, with the inference drawn by
Professors Bradley and Goldsmith – and adopted by Judge
Williams – that if “the international laws of war can inform the
powers that Congress has implicitly granted to the President in the
AUMF, they logically can inform the boundaries of such powers.”
Bradley & Goldsmith, Congressional Authorization, 118 HARV. L.
REV. at 2094. That conclusion about international law setting “the
boundaries” of the President’s authority would, in my view, require
some evidence of congressional intent to that effect, some
consideration of Charming Betsy, some analysis of why
international law trumps the President in resolving statutory
ambiguities, and some analysis of how that conclusion can be
squared with the familiar principles of judicial restraint in the
national security arena articulated in cases such as Egan, Haig v.
Agee, Dames & Moore, Youngstown, and Curtiss-Wright.
 71
international law. After all, such a holding would mean that
every general congressional authorization for war
simultaneously incorporates judicially enforceable limits
based on sometimes vague, contested, or still-evolving
international-law norms that Congress itself has not expressly
enacted into law. (To take one current example, such a
reading of Hamdi might mean that the President’s ordering of
U.S. drone attacks exceeds the President’s authority under the
AUMF. See supra n.21.) It is difficult to imagine that the
Supreme Court would issue such an extraordinary ruling
without careful consideration and extensive discussion of
competing arguments. Yet the question was not even briefed
by the parties or debated at oral argument, much less analyzed
by the plurality opinion. And as I have explained, the Court
never articulated a remotely clear statement along the lines
that Al-Bihani now claims to locate in Hamdi. Just as we
assume Congress does not hide elephants in mouseholes, see
Whitman v. American Trucking Ass’ns, 531 U.S. 457, 468
(2001), we can safely assume the Supreme Court does not do
so either. In short, I would not interpret Hamdi to have issued
such a major pronouncement sub silentio or by indirection.24

In sum, Hamdi is not properly read as applying Charming
Betsy or imposing international-law limits on the scope of the
President’s authority under the AUMF.

F

In this opinion, I have several times reiterated a key
point: To the extent permitted by the Constitution and federal
24
Judge Williams also suggests that Boumediene supports
judicial invocation of international law as a limit on the Executive.
I find nothing in Boumediene to support that proposition or that
speaks to the role of international law in defining the limits of the
AUMF.
 72
statutes, the Executive is free to follow international-law
principles as a matter of policy and to conduct its activities in
accordance with international law. The Executive is also free
to adopt legally binding regulations pursuant to statutory
authorization and may, within the bounds permitted by
statute, seek to correspond those regulations to international-
law principles. A variety of Executive regulations and Army
Field Manuals seek to ensure that the military acts
consistently with certain international-law norms.

But here, we are simply analyzing the contours of a
federal statute, the AUMF, and assessing whether that statute
silently incorporates international law as a limit on the
President’s authority. In considering that issue, an interesting
question arises: Do we give any legal weight to the
Executive’s view on that interpretive matter? The short
answer is no: The Executive Branch’s stance on whether
Charming Betsy applies here (and whether the AUMF
implicitly incorporates international law) is worth examining
only for its persuasive value; it is not entitled to any legal
weight. The Judiciary has the final word on the appropriate
canons of construction or interpretive principles that courts
are to employ in construing statutes.

When interpreting a statute, a court ascertains what the
statute means by looking at the text and employing various
interpretive principles and canons of statutory construction. If
after applying those principles and canons, the court
determines the statute is ambiguous or contains a gap to be
filled, the court determines (sometimes implicitly) the range
of reasonable interpretations of the statute. And then – in
situations where deference to the Executive is considered
appropriate, such as cases implicating national security – the
court defers to the Executive’s authoritative interpretation of
the statute if the Executive’s interpretation falls within that
 73
zone of reasonableness. See Chevron, 467 U.S. at 842-45; cf.
Egan, 484 U.S. at 530. But a gap or ambiguity in a statute
does not relieve a court of its prior duty to interpret the statute
in order to “define the boundaries of the zone of
indeterminacy” in which the Executive is authorized to act.
Michael Herz, Deference Running Riot: Separating
Interpretation and Lawmaking Under Chevron, 6 ADMIN. L.J.
AM. U. 187, 199 (1992). And in performing that duty, the
Court does not defer to the Executive on the question of what
principles or canons of statutory construction to apply or how
to apply them. See, e.g., Solid Waste Agency of N. Cook
County v. U.S. Army Corps of Eng’rs, 531 U.S. 159, 168-70
& n.5 (2001) (taking a different view from the Corps as to the
value of subsequent legislative history in statutory
interpretation).

If the Executive says that legislative history should (or
should not) be considered, that the canon of constitutional
avoidance should (or should not) be invoked, or that the
presumption against implied repeals should (or should not) be
applied, courts don’t simply follow behind the Executive in
lockstep. Courts exercise their own independent judgment on
those canons and interpretive principles.25 The same is true
with respect to the Charming Betsy canon.

25
Indeed, on numerous occasions the Supreme Court has
invoked canons of statutory construction as “part of the plain
meaning inquiry” to determine that the Executive’s interpretation of
a statute fell outside of the zone of statutory ambiguity. WILLIAM
N. ESKRIDGE, JR. ET AL., CASES AND MATERIALS ON LEGISLATION:
STATUTES AND THE CREATION OF PUBLIC POLICY 1257-58 (4th ed.
2007); see, e.g., Edward J. DeBartolo Corp. v. Fla. Gulf Coast
Bldg. & Constr. Trades Council, 485 U.S. 568, 574-75 (1988)
(rejecting agency’s interpretation as contrary to the canon of
constitutional avoidance). If the Court instead allowed the agency
to dictate which canons apply, the Court would not be able to
 74

Take an example. Assume arguendo that the AUMF is
ambiguous as to whether it authorizes targeted killing of al
Qaeda members whose conduct does not rise to the level of
“direct participation in hostilities.” If so, the Executive,
motivated by international-law concerns, may choose to
interpret the AUMF either to authorize or not to authorize
targeted killing of al Qaeda members who are not direct
participants in hostilities. Cf. Kristen E. Eichensehr, On
Target? The Israeli Supreme Court and the Expansion of
Targeted Killings, 116 YALE L.J. 1873 (2007). And in a
justiciable case, courts will defer to that reasonable Executive
interpretation – at least unless it contravenes another statute.
But that is quite different from the Executive telling the court
what canons of construction the court must employ in
defining what the AUMF authorizes and permits in the first
place.

Having explained that the Executive Branch’s views on
the applicability of the Charming Betsy canon matter only for
their persuasive weight, the next question is: What in fact are
the Executive’s views on the Charming Betsy canon as
applied to a statute like the AUMF? At the moment, that is
unclear.

The Executive – speaking through the Office of Legal
Counsel – has long maintained that the Charming Betsy canon
is “wholly inapposite” to the interpretation of “broad
authorizing statutes” like the AUMF that “‘carry[] into
Execution’ core Executive powers.” 13 Op. Off. Legal
Counsel 163, 172 (1989) (quoting U.S. CONST. art. I, § 8, cl.
18). The Executive has declared that in the absence of

perform its role in defining the boundaries of permissible agency
interpretation.
 75
express congressionally imposed limitations, “general
enabling statutes” of that kind should be presumed to grant
authority “commensurate with” the President’s constitutional
powers. Id. And, the Executive has stated, that presumption
“is all the more compelling where . . . the President’s foreign
relations powers are implicated.” Id.; see also Bradley,
Chevron Deference, 86 VA. L. REV. at 699 (discussing and
endorsing the Executive Branch’s analysis).

The Executive – speaking through the Solicitor General –
has also repeatedly reiterated that position about Charming
Betsy in litigation before the Supreme Court. See Gov’t Br. at
36 n.11, Hamdan v. Rumsfeld, 548 U.S. 557 (2006) (No. 05-
184) (“this Court has never applied the Charming Betsy canon
to invalidate a presidential action that was taken in express
reliance on a federal statute and involves the exercise of the
President’s core authority as Commander in Chief”); Reply
Brief for the United States at 3, Sosa, 542 U.S. 692 (No. 03-
485) (“the canon does not apply to a statute . . . that authorizes
conduct by the branch of government most directly
responsible for the conduct of foreign affairs and involves a
core power of the Executive Branch”).

In its brief in opposition to Al-Bihani’s rehearing
petition, the Executive Branch does not refer to the prior
Executive Branch position. And it’s unclear from its brief
where the Government currently stands on this question. In
the text of its brief, the Government says that international
law “inform[s]” interpretation of the AUMF and that this
view is “consistent with” Charming Betsy. Gov’t Response to
Pet. for Reh’g and Reh’g En Banc at 7. Notably, however,
the Government’s brief does not say that international law
limits the AUMF or that Charming Betsy applies to the
AUMF. Moreover, footnote 3 of the Government’s brief
states that “[w]here the laws of war are unclear or analogies to
 76
traditional international armed conflicts are inapt, a court
should accord substantial deference to the political branches
in construing how the laws of war apply to this nontraditional
conflict.” Id. at 8 n.3. In light of the uncertainty surrounding
many international-law norms, and given the numerous ways
in which the current U.S. war against al Qaeda and the
Taliban diverges from the traditional model of international
armed conflict, courts following the approach suggested in
footnote 3 of the Government’s brief would routinely defer to
the Executive’s decision whether and how international law
applies. The Government’s position in footnote 3 is therefore
entirely inconsistent with the understanding of the Charming
Betsy canon advanced, for example, in the brief of the amici.
Whatever the text of the Government’s brief may appear to
give, footnote 3 takes away. The Government’s brief thus
seems to erect a Potemkin Charming Betsy and to represent
only a cosmetic change from the prior Executive Branch
position on how Charming Betsy applies.

Insofar as the Government actually takes the position that
courts must enforce international-law limits on the President’s
authority under the AUMF, that position prompts an
observation: If the Executive wants to comply with
international-law norms and believes it is detaining someone
in violation of international law, it can simply release that
person (at least to another country). See, e.g., Munaf v.
Geren, 128 S. Ct. 2207 (2008); Kiyemba v. Obama, 561 F.3d
509 (D.C. Cir. 2009). No court has forced or is forcing the
Executive to hold these detainees. The courts are simply
ruling on whether the Executive is authorized under U.S. law
to hold the detainees.

In short, it is not evident that the Executive Branch’s
currently articulated position on Charming Betsy differs from
 77
its longstanding position. In any event, its position receives
no special deference, so we need not decipher it further.26

26
In considering the views of the Executive on legal questions
affecting government power, courts must exercise care that the
concessions of one Executive do not inappropriately bind future
Executives. In court, the Executive Branch does not always press
the most expansive possible argument in support of its legal
authority – whether for reasons of policy, politics, litigation
strategy, international concern, or otherwise. Courts must be
careful before enshrining such concessions into binding judicial
precedent protected by stare decisis that a future Executive could
not readily undo. As the Supreme Court recently explained in a
different context: “Perhaps an individual President might find
advantages in tying his own hands. But the separation of powers
does not depend on the views of individual Presidents, nor on
whether the encroached-upon branch approves the encroachment.
The President can always choose to restrain himself . . . . He
cannot, however, choose to bind his successors by diminishing their
powers, nor can he escape responsibility for his choices by
pretending that they are not his own.” Free Enterprise Fund v.
Pub. Co. Accounting Oversight Bd., 130 S. Ct. 3138, 3155 (2010)
(citations and internal quotation marks omitted).
Rather than accepting concessions, the Supreme Court on
occasion has found that the law (either constitutional or statutory) is
more favorable to the Executive than the Executive itself asserted in
litigating the particular case. See, e.g., Free Enterprise Fund, 130
S. Ct. 3138; Davis v. United States, 512 U.S. 452, 461-62 (1994)
(declining to adopt a rule “requiring officers to ask clarifying
questions” when a suspect makes an “ambiguous or equivocal”
request for counsel, although the Government had argued in its
brief that such a rule would be appropriate); Freytag v. Comm’r,
501 U.S. 868, 879-80 (1991) (declining to “defer to the Executive
Branch’s decision” that statute allowing Chief Judge of Tax Court
to appoint trial judges did not encroach upon “Presidential
prerogatives under the Appointments Clause”); see also Nixon v.
Adm’r of Gen. Servs., 433 U.S. 425, 491 (1977) (Blackmun, J.,
concurring in part and concurring in judgment) (“incumbent
 78

III

Suppose that the above analysis of Hamdi or Charming
Betsy is wrong and that the President’s authority under the
AUMF is in fact limited by international law. It nonetheless
would not follow that the President would be subject to
judicially enforceable international-law limits when
commanding the U.S. war effort and detaining captives such
as Al-Bihani. That is because the President possesses
independent authority under Article II of the Constitution to
act against al Qaeda and the Taliban – and to detain members
of those groups – even without congressional authorization.
Article II constitutes an alternative source of authority that the
Hamdi Court did not need to – and did not – consider. See
Hamdi v. Rumsfeld, 542 U.S. 507, 517 (2004) (plurality
opinion of O’Connor, J.) (“We do not reach the question
whether Article II provides such authority . . .
because . . . Congress has in fact authorized Hamdi’s
detention, through the AUMF.”).

To appreciate that Article II point, it is useful to recount
the framework for judicial review of presidential actions in
the national security and foreign policy arena set forth by
Justice Jackson in his landmark opinion in Youngstown Sheet
& Tube Co. v. Sawyer, 343 U.S. 579 (1952); see also
Medellín v. Texas, 552 U.S. 491, 524-25 (2008) (applying
framework); Dames & Moore v. Regan, 453 U.S. 654, 668-69
(1981) (same). According to Justice Jackson, presidential

President’s submission, made through the Solicitor General, that
the Act serves rather than hinders the Chief Executive’s Art. II
functions” is not “dispositive of the separation-of-powers issue”);
id. at 556-57 (Rehnquist, J., dissenting) (“the principle of separation
of powers . . . . may not be signed away by the temporary
incumbent of the office which it was designed to protect”).
 79
actions can be divided into three categories, each with
different constitutional implications:

 In Category One, the President acts pursuant to a
congressional authorization, and his authority is
therefore “at its maximum.” Youngstown, 343 U.S. at
635 (Jackson, J., concurring). Courts will uphold a
presidential action in Category One so long as that
action is within the power of the federal government
as a whole. Id. at 636-37.

 In Category Two, the President acts in the absence of
“either a congressional grant or denial of authority.”
Id. at 637. A presidential action that falls in Category
Two is not affirmatively authorized by Congress, but
neither is it prohibited. The President is therefore
operating in what Justice Jackson called a “zone of
twilight.” Id.

 In Category Three, the President acts in contravention
of the will of Congress, and his authority is therefore
“at its lowest ebb.” Id. Courts will strike down a
presidential action in Category Three unless the
Constitution gives the President exclusive, preclusive
authority to take the challenged action. Id. at 637-38;
see David J. Barron & Martin S. Lederman, The
Commander in Chief at the Lowest Ebb – Framing
the Problem, Doctrine, and Original Understanding,
121 HARV. L. REV. 689, 693-94 (2008).

In this case, the President’s exercise of detention
authority pursuant to the AUMF is properly understood as
falling within Category One of Justice Jackson’s Youngstown
framework, regardless of whether the President has exercised
that authority in compliance with international law. The
 80
AUMF broadly authorizes the President to use military force
against al Qaeda and the Taliban. “Force” includes at least all
the traditional and fundamental tools of warfare, including
detention of enemy personnel. That grant of authority also
affords the President discretion to reasonably define the class
of enemy personnel subject to military detention. Cf. Holder
v. Humanitarian Law Project, 130 S. Ct. 2705, 2727-28
(2010) (courts defer to factual inferences drawn by the
Executive “in connection with efforts to confront evolving
threats in an area where information can be difficult to obtain
and the impact of certain conduct difficult to assess”).
Neither the AUMF’s text nor its legislative history suggests
that Congress intended to authorize the President to take only
those actions approved by international law; and that silence
is instructive given that, as the Supreme Court has recognized,
“Congress knows how to accord domestic effect to
international obligations when it desires such a result.”
Medellín, 552 U.S. at 522.

But if that is incorrect and if, as Al-Bihani and amici
contend, the AUMF does not authorize the President to take
actions that are prohibited by international law, then
presidential actions contrary to international law would lack
congressional authorization. Therefore, such actions would
not fall within Justice Jackson’s Category One.

But even so, it is important to appreciate that such actions
then would merely fall into Category Two of Justice
Jackson’s Youngstown framework, not Category Three. The
AUMF certainly does not prohibit the President from
violating international law, such that doing so would make
this a Category Three situation. As Professors Bradley and
Goldsmith have correctly explained, the AUMF “is a broadly
worded authorizing statute; it does not purport to prohibit the
President from doing anything, much less from violating the
 81
laws of war.” Curtis A. Bradley & Jack L. Goldsmith,
Congressional Authorization and the War on Terrorism, 118
HARV. L. REV. 2047, 2097 (2005).

Therefore, if Al-Bihani and amici are correct in their
reading of Hamdi or Charming Betsy, then presidential
actions contrary to international law are neither authorized nor
prohibited by the AUMF – and as a result would fall within
the “twilight” of Justice Jackson’s Category Two.

The proper Category Two analysis in these circumstances
supports the President. Courts generally will not circumscribe
the President’s authority to take action in defense of the
Nation – at least action against non-citizens abroad – “unless
Congress specifically has provided otherwise” or the action
contravenes other constitutional limits. Dep’t of the Navy v.
Egan, 484 U.S. 518, 530 (1988); see also The Prize Cases, 67
U.S. 635, 668 (1862) (“If a war be made by invasion of a
foreign nation, the President . . . . is bound to accept the
challenge without waiting for any special legislative
authority.”). As Justice Jackson stated in Youngstown, courts
should “indulge the widest latitude of interpretation to sustain
[the Commander in Chief’s] exclusive function to command
the instruments of national force, at least when turned against
the outside world for the security of our society.” 343 U.S. at
645 (Jackson, J., concurring); cf. Dames & Moore, 453 U.S.
at 686 (“a systematic, unbroken, executive practice, long
pursued to the knowledge of the Congress and never before
questioned . . . may be treated as a gloss on ‘Executive
Power’ vested in the President by § 1 of Art. II”) (quoting
Youngstown, 343 U.S. at 610-11 (Frankfurter, J.,
concurring)).27

27
Here, as in any Category Two situation, it is important to
reiterate that Congress has the power to move the case to Category
 82

To be sure, in domestic administrative law, with a few
constitutionally based exceptions, the Executive is generally
barred from taking action that is not within the scope of an
affirmative congressional authorization. But when the
President acts extraterritorially against non-U.S. citizens in
self-defense of the Nation, especially in support of a war
effort that Congress has authorized, that default assumption is
reversed. In that realm, the President possesses broad
authority under Article II, as Chief Executive of the Nation
and Commander in Chief of the Armed Forces, that does not
depend on specific congressional authorization.

There are many examples in recent years of Presidents’
invoking their Article II authority to act without specific
congressional authorization in the national security realm. In
1995, President Clinton deployed troops to Bosnia without
congressional authorization, citing only his independent
Article II authority “as Commander in Chief and Chief
Executive.” President Clinton again acted without
congressional authorization when he ordered air strikes in
Kosovo in 1999. Similarly, President George W. Bush
invoked only his Article II authority when he deployed U.S.
military forces to Haiti without congressional authorization in
2004. See Letter to Congressional Leaders on the
Deployment of United States Military Forces for
Implementation of the Balkan Peace Process, 2 PUB. PAPERS
OF WILLIAM J. CLINTON 1856-57 (Dec. 6, 1995); Letter to
Congressional Leaders Reporting on Airstrikes Against
Serbian Targets in the Federal Republic of Yugoslavia (Serbia

Three by prohibiting or limiting the presidential action in question.
In other words, any conclusion about the President’s authority in
Category Two does not disable Congress from legislating on the
issue in question, and thereby restricting the President’s authority,
to the extent permitted by the Constitution.
 83
and Montenegro), 1 PUB. PAPERS OF WILLIAM J. CLINTON
459-60 (Mar. 26, 1999); Letter to Congressional Leaders on
the Further Deployment of United States Military Forces in
Haiti, 1 PUB. PAPERS OF GEORGE W. BUSH 295-96 (Mar. 2,
2004).28

28
Under Article II, the President possesses significant
authority to act without congressional authorization in the national
security and foreign policy realms (that is, to act in Youngstown
Category Two). At least in its basic outlines, that proposition is
generally accepted.
Although not directly relevant to the discussion here, it bears
mention for purposes of analytical clarity that the President also has
some lesser authority – albeit largely undefined – to act not only
without congressional authorization but also over a congressional
prohibition (that is, to act in Youngstown Category Three). This is
known as the President’s exclusive, preclusive authority. The
precise scope of that authority is highly controversial and is, as
Justice Jackson rightly explained, a sensitive and weighty question.
See Youngstown, 343 U.S. at 637 (Jackson, J., concurring); see also
Barron & Lederman, The Commander in Chief at the Lowest Ebb –
Framing the Problem, Doctrine, and Original Understanding, 121
HARV. L. REV. at 693-94.
As scholars have catalogued, Presidents throughout history
have often asserted power in Category Two and on occasion even
in Category Three. See David J. Barron & Martin S. Lederman,
The Commander in Chief at the Lowest Ebb – A Constitutional
History, 121 HARV. L. REV. 941, 1098 (2008) (from 1950 through
2008, “every President, save for Carter, invoked” exclusive,
preclusive executive war powers “in one form or another”); JOHN
YOO, CRISIS AND COMMAND: A HISTORY OF EXECUTIVE POWER
FROM GEORGE WASHINGTON TO GEORGE W. BUSH 402 (2009)
(Presidents “have often wielded their powers in the face of
congressional silence, and sometimes they have acted contrary to
Congress to advance what they perceived to be the national
interest”); see, e.g., Letter to Congressional Leaders Reporting on
Military Action Against Terrorist Sites in Afghanistan and Sudan, 2
PUB. PAPERS OF WILLIAM J. CLINTON 1464 (Aug. 21, 1998)
 84

For purposes of considering the President’s power to
detain suspected members of al Qaeda or the Taliban even
without congressional authorization (that is, in Category
Two), perhaps the most relevant historical precedent is
President Clinton’s bombing of suspected al Qaeda targets in
Afghanistan and Sudan in 1998. In ordering those military
strikes, President Clinton relied solely on his Article II
authority. See Letter to Congressional Leaders Reporting on
Military Action Against Terrorist Sites in Afghanistan and
Sudan, 2 PUB. PAPERS OF WILLIAM J. CLINTON 1464 (Aug. 21,
1998). President Clinton thus took action without
congressional authorization to kill non-U.S.-citizens abroad
whom he determined to be members or facilitators of al
Qaeda; that action certainly suggests that the President
possesses at least some lesser included authority under Article
II to detain such individuals without congressional
authorization.29

(asserting constitutional authority to order military strikes against
terrorists abroad in the absence of congressional authority, that is,
in Category Two); U.S. DEPARTMENT OF JUSTICE, LEGAL
AUTHORITIES SUPPORTING THE ACTIVITIES OF THE NATIONAL
SECURITY AGENCY DESCRIBED BY THE PRESIDENT 3, 34-35 (2006)
(asserting in the alternative that the President possesses
constitutional authority to order the NSA to intercept certain
terrorist communications even in the face of a congressional
prohibition, in other words, that such presidential power is
exclusive and preclusive and that the President prevails in Category
Three); see also In re Sealed Case, 310 F.3d 717, 742 (FISA Ct.
Rev. 2002) (“We take for granted that” Congress “could not
encroach on the President’s constitutional power” to “conduct
warrantless searches to obtain foreign intelligence information” – in
other words, that such presidential power is exclusive and
preclusive and that the President prevails in Category Three).
29
This analysis of Youngstown Category Two does not mean
the President has the authority to initiate, for example, a large-scale
 85

In exercising his Article II Commander-in-Chief
authority, the President is not subject to judicially enforceable
international-law limitations. Nowhere does the Constitution
require the President to comply with foreign or international
law. “[U]nder our Constitutional jurisprudence,” an “action
by the President . . . that is within [his] constitutional
authority does not become a violation of the Constitution
because the Act places the United States in violation of a
treaty provision or of a U.S. obligation under customary law.”
LOUIS HENKIN, FOREIGN AFFAIRS AND THE UNITED STATES
CONSTITUTION 236 (2d ed. 1996). And in its recent decision
in Medellín, the Supreme Court decisively held that the
President’s “responsibility to ‘take Care that the Laws be
faithfully executed’” applies only to “domestic law.” 552
U.S. at 532 (quoting U.S. CONST. art. II, § 3). There is no
basis, moreover, for thinking that international-law norms
independently equate to congressional prohibitions for
purposes of putting a presidential action in Category Three.
In his comprehensive Youngstown opinion, Justice Jackson

offensive ground war without congressional authorization. The
initiation of war – particularly an offensive ground war where
American casualties are likely to be significant – arguably presents
a constitutional question different in kind because the Constitution
specifically assigns to Congress the power to declare war. See U.S.
CONST. art. I, § 8, cl. 11; THE FEDERALIST NO. 69, at 416
(Alexander Hamilton) (Clinton Rossiter ed., rev. ed. 1999); Letter
from George Washington to William Moultrie (Aug. 28, 1793).
For present purposes, it is enough to point out that, even without
specific congressional authorization, the President has
constitutional authority to take steps against non-citizens abroad to
support a congressionally authorized war or to take shorter-term
actions against non-citizens abroad in order to protect the Nation, at
least unless the Constitution or a constitutionally permissible
federal statute prohibits the action in question.
 86
never suggested that courts should constrain the President’s
exercise of war powers based on international law. Not
surprisingly, therefore, “[t]he Supreme Court has never
invalidated presidential action on the ground that the action
violated the laws of war.” Bradley & Goldsmith,
Congressional Authorization, 118 HARV. L. REV. at 2097
n.220. Indeed, “[i]f the Commander in Chief Clause itself
incorporates evolving law-of-war restrictions, the scope of the
Commander-in-Chief power would have shrunk significantly
during the past two centuries, which is contrary to
constitutional history.” Id.

Thus, even if the AUMF incorporates international-law
limitations on the President’s authority, Article II does not. In
the final analysis, then, it ordinarily would make little
difference whether the AUMF incorporates international-law
norms as a limit on the scope of the President’s statutory
authorization, because Article II would still independently
authorize the President’s action. It would make a difference
in this case, but only because the Executive Branch no longer
is asserting Article II as a basis for detaining Al-Bihani and
other Guantanamo detainees. Therefore, Al-Bihani and other
Guantanamo detainees will prevail in litigation and win their
release if the AUMF does not authorize their detention, even
if Article II of the Constitution would authorize it.30

30
President Bush and President Clinton asserted independent
Article II authority to take action against al Qaeda. See Letter to
Congressional Leaders Reporting on Military Action Against
Terrorist Sites in Afghanistan and Sudan, 2 PUB. PAPERS OF
WILLIAM J. CLINTON 1464 (explaining that President Clinton had
ordered strikes against al Qaeda terrorist camps in Afghanistan
“pursuant to my constitutional authority to conduct U.S. foreign
relations and as Commander in Chief and Chief Executive”); Gov’t
Br. at 19, Hamdi, 542 U.S. 507 (No. 03-6696) (asserting that
Article II authorized President Bush to wage war in response to the
 87

* * *

In sum, courts enforce constitutionally permissible
constraints imposed by Congress on the President’s war
powers, including those that Congress might derive from
international-law principles. Courts likewise enforce
judicially manageable constraints imposed by the U.S.
Constitution on the President’s war powers. In addition, the
Executive Branch within its constitutional and statutory
bounds may decide, as a matter of international obligation or
policy, to follow non-self-executing treaties and customary-
international-law norms. But all of that is far different from a
court on its own invoking international-law principles to
restrict the President’s direction and management of the war
effort. Under our Constitution, it is for the political branches
in the first instance to incorporate international-law norms
into domestic U.S. law. Congress did not do so when
enacting the AUMF. In asking us to nonetheless rely on
international-law principles to order Al-Bihani’s release from
U.S. military custody, the argument of Al-Bihani and amici
contravenes bedrock tenets of judicial restraint and separation
of powers.

September 11th attacks and detain enemy combatants in connection
with that war without “any special legislative authority”) (quoting
The Prize Cases, 67 U.S. at 668). Even though the current
Administration has chosen not to assert its Article II authority
before the courts in these Guantanamo cases, it has not argued that
the President does not possess detention authority under Article II,
nor has it suggested that any such authority would be limited by
international law.
 WILLIAMS, Senior Circuit Judge: The only serious claim
in appellant’s petition for en banc review, a claim backed by
amici non-governmental organizations and scholars, argues
that the panel improperly failed to consider the possible
impact of international law on the President’s authority under
the Authorization for the Use of Military Force, Pub.L. No.
107–40 § 2(a), 115 Stat. 224, 224 (2001) (reprinted at 50
U.S.C. § 1541 note) (the “AUMF”). I made clear in my
separate opinion why Al Bihani’s detention was plainly
lawful, so that it was unnecessary here to address in general
terms the potential role of international law in such cases. Al-
Bihani v. Obama, 590 F.3d 866, 885 (D.C. Cir. 2010). I
continue to believe that that was correct, and for the same
reasons. See also Opinion of Sentelle, C.J., and Ginsburg,
Henderson, Rogers, Tatel, Garland and Griffith, JJ.,
concurring in denial of rehearing en banc (“[T]he panel’s
discussion of that question is not necessary to the disposition
of the merits.”).

In connection with the denial of rehearing, Judge
Kavanaugh has filed an extensive scholarly analysis of
whether international law, in the form of customary
international law or non-self-executing treaties, can ever
properly influence a United States court to find authority
granted by statute to the President narrower than it otherwise
would. I commend Judge Kavanaugh’s exposition to all.
While I agree with much of it, my disagreement on certain
points seems worth stating.

I follow Judge Kavanaugh in distinguishing analytically
between elements of international law embodied specifically
in statutes or in self-executing treaties and elements in the
form of customary international law or non-self-executing
treaties. See Kavanaugh Op. at 8. It is only the latter that
concern us here; I will for simplicity’s sake refer to them as
“international law” or some close approximation.
 2
Judge Kavanaugh, I think, fails to adequately distinguish
between treatment of international law norms as “judicially
enforceable limits” on Presidential authority, id. at 1, or as
“domestic U.S. law,” id. at 8, and use of such norms as a
“basis for courts to alter their interpretation of federal
statutes,” id. at 47. By “alter their interpretation,” I take
Judge Kavanaugh to mean (as I said above) for a court to
allow international law to persuade it to adopt a narrower
interpretation of the President’s authority than it would
otherwise have chosen. I will assume that Judge Kavanaugh
is correct as to the impropriety of the stronger use of
international law (treating it as “domestic law”), but I believe
him incorrect on the weaker (allowing it to affect a court’s
statutory interpretation).

Courts use a wide range of information outside the words
of a statute to find those words’ meaning. This reflects the
simple truth that the question of a word’s meaning is an
empirical one: what have persons in the relevant community
actually meant when using the words that appear in a statute?
Among the most obvious outside sources to resolve that
question are legislative history, usage in other laws and in
judicial decisions, and dictionaries. Courts use all three
incessantly. Dictionaries, of course, are only scholars’ claims
as to how people have historically used the words in question.
Because military conflict is commonly an international
phenomenon, words relating to such conflict are used in
international discourse, of which international law is a subset.
That international law has a normative element is nothing
special; virtually all laws do—yet laws represent widely
known public uses of language that legislatures often
repackage in novel combinations and contexts. It would be an
odd member of Congress who supposed that in authorizing
the use of military force he was embracing uses equivalent to
all such uses that have ever occurred: think Nanking 1937-38;
 3
Katyn 1940; Lidice 1942; My Lai 1968. More generally, it
seems improbable that in authorizing the use of all “necessary
and appropriate force” Congress could have contemplated
employment of methods clearly and unequivocally
condemned by international law.

Judge Kavanaugh agrees with that conclusion, but argues
that we infer such limits on Congress’s grant of power simply
from penalties or prohibitions in domestic law. See id. at 44-
45. He is surely correct that this is one source for finding
limits on an authorization of military force, but that does not
make it the only legitimate source of such limits. In some
circumstances, Judge Kavanaugh’s “domestic U.S. law of
war,” id. at 43 n.14, may have relatively little to say on a
question that international practice has addressed for
centuries. It obviously seemed so to the Supreme Court in
Hamdi v. Rumsfeld, 542 U.S. 507, 518-21 (2004), where the
plurality looked to international norms on the question of
whom the President may detain pursuant to the AUMF, and
for how long.

Before Erie R.R. Co. v. Tompkins, 304 U.S. 64 (1938),
U.S. courts undoubtedly used international law to help resolve
cases. See Kavanaugh Op. at 16. It appears to have been
uncontroversial for international law to serve not only as a
species of federal general common law, binding absent
contrary domestic law, see id. at 16-17, but also as a source of
interpretive guidance regarding statutes passed by Congress,
see, e.g., Brown v. United States, 8 Cranch 110, 124-28
(1814) (Marshall, C.J.) (interpreting the domestic legal effects
of a U.S. declaration of war in part by reference to
international norms, along with constitutional principles and
domestic statutes). To dispute that commonsensical
understanding, after all, requires defending the unlikely view
that international law—unlike other known binding laws—
 4
offered no useful information whatsoever regarding the
meaning of new laws on similar subjects. In Judge
Kavanaugh’s view, Erie effectively proscribed use of
international law as “enforceable” U.S. law. See Kavanaugh
Op. at 17. But that landmark case left intact the pre-existing
alternative role of international law as a store of information
regarding the sense of words Congress enacts into laws
governing international matters—a role that never depended
on international law’s being a form of federal general
common law (which Erie famously banished). Erie hardly
requires that every last source of information regarding the
meaning of words in statutes be an enacted law; if it does,
federal courts have been disobeying its command for more
than seven decades.

Even Judge Kavanaugh appears to acknowledge that
international law may in some circumstances properly shape a
court’s interpretation of a federal statute. If I understand him
correctly, though, he accepts reliance on international law to
expand the meaning of a statutory grant of executive authority
but never to contract it (the benchmark being the reading the
court would otherwise have reached). See Kavanaugh Op. at
69; id. at 70 n.23. Use of international law as a one-way
ratchet seems to me illogical. As Curtis Bradley and Jack
Goldsmith put it in Congressional Authorization and the War
on Terrorism, if the international laws of war “can inform the
powers that Congress has implicitly granted to the President
in the AUMF, they logically can inform the boundaries of
such powers.” 118 Harv. L. Rev. 2047, 2094 (2005). To
whatever extent the international laws of war shed light on
what the AUMF lets the President do, they shed light in all
directions, not just one. If international law supports finding a
grant of the “X” power (a power that by hypothesis the court
would not otherwise have found), it must support some
inquiry into what “X” means.
 5

The plurality’s ruling in Hamdi uses international law as
an interpretive tool in the way I’ve described. There the
petitioner contended that the AUMF simply didn’t authorize
detention of U.S. citizens. Four justices of the Supreme Court
agreed. 542 U.S. at 551 (Souter, J., concurring in part,
dissenting in part) (“I conclude . . . that the Government has
failed to support the position that the Force resolution
authorizes the described detention of Hamdi[.]”); id. at 574
(Scalia, J., dissenting) (“Contrary to the plurality’s view, I do
not think this statute [the AUMF] even authorizes detention of
a citizen[.]”). Four others disagreed, reasoning that the
AUMF was a classic authorization for the use of force, and
that incident to such authorizations, states almost invariably
enjoy the right to detain certain captured individuals. But the
plurality made explicit that the detention authority that is a
standard tool for states authorized to use force is by no means
unlimited: “Certainly, we agree that indefinite detention for
the purpose of interrogation is not authorized. Further, we
understand Congress’ grant of authority for use of ‘necessary
and appropriate force’ to include the authority to detain for
the duration of the conflict, and our understanding is based on
longstanding law-of-war principles.” See id. at 521 (plurality
opinion). Thus the plurality answered Hamdi’s concern about
indefinite duration by saying that the detention authority
recognized under the law of war, and thus implicitly conferred
by the AUMF, was subject to a limit similarly recognized by
the law of war.

All of this said, I want to make clear that I agree with
Judge Kavanaugh that the President’s interpretation of such
an authorizing statute is owed “great weight,” the phrase I
used in my separate opinion in Hamdan v. Rumsfeld, 415 F.3d
33, 44 (D.C. Cir. 2005), rev’d 548 U.S. 557 (2006). I do not
 6
see much if any daylight between “great weight” and the
Chevron deference that Judge Kavanaugh invokes.1

Thus, when an Article III court is for some reason
adjudicating the validity of executive military conduct (an
issue to which I return below), and there is uncertainty as to
whether the conduct fell within the statutory language, I
would expect the court to ask what limits the statute clearly
set on its grant of authority. In doing so the court would use
all the traditional means of statutory interpretation to flesh out
the statutory boundaries. See I.N.S. v. Cardoza-Fonseca, 480
U.S. 421, 446 (1987). These would include historical uses of
the terms in relevant contexts, including the discourse of

1
The Obama administration’s interpretation of the AUMF is that
international law does illuminate the outer bounds of the authority
conferred by the statute. See Resp. to Pet. for Rehearing at 6-7
(“[T]he panel's . . . statements that the laws of war do not limit the
President's authority under the AUMF . . . do[] not properly reflect
the state of the law.”); Harold Hongju Koh, Legal Adviser, U.S.
Department of State, The Obama Administration and International
Law: Address at the Annual Meeting of the American Society of
International Law (Mar. 25, 2010) (text available on the website of
the U.S. Department of State at
http://www.state.gov/s/l/releases/remarks/139119.htm) (last viewed
Aug. 3, 2010) (“[T]his Administration has expressly acknowledged
that international law informs the scope of our detention authority.
Both in our internal decisions about specific Guantanamo detainees,
and before the courts in habeas cases, we have interpreted the scope
of detention authority authorized by Congress in the AUMF as
informed by the laws of war.”) (emphasis in original). While Judge
Kavanaugh treats the government’s view of the AUMF as a matter
of how to interpret the statute (and therefore one within the
discretion of the judiciary in the first instance), the Executive’s
position seems more accurately viewed as an interpretation of the
statute in its own right (and thus worthy of our deference). Cf.
Kavanaugh Op. at 72-77.
 7
international law. Only conduct beyond the words’ clearly
established meaning would be off-limits.

Moreover, I should not be taken as saying that courts
should take uncertain or disputed propositions of international
law and build them into iron constraints on the meaning of
congressional grants of authority. Judge Kavanaugh is quite
right to quote Gouverneur Morris’s observation that
international law is “often too vague and deficient to be a
rule” without implementing legislation. Kavanaugh Op. at 9.
Courts should approach seemingly authoritative declarations
of international law with caution. Even the highest
international tribunals appear at times to be influenced in their
rulings by the favor in which the disputing nations are held in
international circles. Cf. H.R. Res. 713, 108th Cong. (2004)
(denouncing the July 9, 2004 decision of the International
Court of Justice in the Hague purporting to find Israel’s
construction of a barrier at the time of the Second Intifada a
violation of international law). Thus U.S. courts should not
automatically attach weight to rulings of such tribunals, not to
mention less authoritative expressions of international law, in
the absence of clear reason to believe that they will be
consistently and evenhandedly applied, are the product of
serious reasoning and are susceptible of practical application.

Finally, Judge Kavanaugh is plainly concerned about the
propriety of Article III courts using gauzy notions of
international law to rein in the executive’s conduct of military
operations. I share that concern. But under Boumediene,
Article III courts evaluate the propriety of the detention of
non-U.S. nationals. In doing so they necessarily pass
judgment on the admissibility of evidence collected on the
battlefield, and thus on the propriety of the methods used for
such collection. District courts have been doing so regularly
since Boumediene. They therefore monitor, and to a degree
 8
supervise, the battlefield conduct of the U.S. military. But
that is a consequence of Boumediene, in which the federal
judiciary assumed an entirely new role in the nation’s military
operations; it is not a product of international law’s role in
understanding congressional grants of power—a separate
matter entirely.