After pleading guilty to a violation of 18 U.S.C. § 1470, for transferring obscene material to a minor,1 Matthew Mason Dodge (“Dodge”) appeals from the part of the district court’s judgment that requires him to register as a Tier I Sex Offender under the Sex Offender Registration and Notification Act (“SORNA”), 42 U.S.C. § 16911. We reverse. Although Dodge transmitted obscene material to persons he believed to be minors, he did not engage in conduct that constitutes a “sex offense against a minor,” 42 U.S.C. § 16911(7)(I) (emphasis added), as we understand that phrase. Although we do not adopt Dodge’s construction of SORNA, we conclude that we are unable to distinguish Dodge’s behavior from other behavior, involving distributing obscene material, that would support a conviction under 18 U.S.C. § 1470, but would not require Dodge to register as a sex offender. Accordingly, Dodge also cannot be required to register.
Background
Over a period of approximately one year, Matthew Dodge, on a number of occasions, interacted on internet chat-rooms with persons he took to be young girls aged 13-14 years old. On at least three occasions, Dodge either emailed photographs of himself fully nude and/or masturbating or provided a link to such photos. On at least two occasions, Dodge sent video images of himself masturbating or fondling his genitals to individuals he took to be minors below the age of 16.2
Because of this conduct, Dodge was indicted on three counts of knowingly transferring obscene materials to individuals under the age of 16 in violation of 18 U.S.C. § 1470.3 Dodge entered a guilty plea, without a plea agreement, and agreed that the government could prove the alleged facts. The government, by motion, dismissed Counts Two and Three at sentencing, leaving Dodge to be sentenced only for the first count. Dodge was then sentenced to 18 months in prison. At sentencing, the District Court also ordered a three year term of supervised release and ordered Dodge, as a “Tier 1 Sex Offender,” to register under SORNA “for up to life.” The District Court concluded that the expansion of the definition of “sex offense” under 42 U.S.C. § 16911(5)(A)(ii) and (7)(I),4 to include any criminal offense *1360that is a specified offense against a minor, where the conduct in question is “by its nature a sex offense against a minor,” applied to Dodge’s offense, requiring him to register. It is this conclusion that Dodge appeals.
Standard of Review
We review terms of supervised release for abuse of discretion. See United States v. Nash, 438 F.3d 1302, 1304 (11th Cir.2006). We review a district court’s interpretation of a statute de novo. United States v. Prosperi, 201 F.3d 1335, 1342 (11th Cir.2000).
Discussion
We begin with relevant provisions of the statute. Specifically, if Dodge is required to register as a sex offender under SOR-NA it can only be because he was convicted of a “sex offense” that is a “criminal offense that is a specified offense against a minor.” 42 U.S.C. § 16911(5)(ii). No other subpart of subsection (5) applies to the charge to which Dodge plead guilty, a violation of 18 U.S.C. § 1470.5 Following subsection (5), a “[c]riminal offense” and a “specified offense against a minor” are further defined in 42 U.S.C. § 16911(6) and (7) respectively. We will consider each subsection in turn in order to determine how each definition may apply to Dodge’s violation.
First, because 18 U.S.C. § 1470 is not a “State, local, tribal, foreign, or [specified] military offense,” a violation of 18 U.S.C. § 1470 is only covered by subsection (6) of § 16911 if it is an “other criminal offense.” Claiming that a violation of 18 U.S.C. § 1470 is not an “other criminal offense” for purposes of subsection (6), Dodge argues that federal offenses that qualify as *1361sex offenses are enumerated, or “specified” as a “sex offense,” by 42 U.S.C. § 16911(5)(iii), and because 18 U.S.C. § 1470 is not so enumerated, the principle of expressio unius est exlusio alterius requires us to hold that non-enumerated federal crimes, including violations of 18 U.S.C. § 1470, are not “sex offenses” for the purpose of 42 U.S.C. § 16911.6 Application of the expressio unius canon, however, would make unclear the meaning or referent in subsection (6) for “other criminal offenses.” Nonetheless, Dodge’s argument is not without merit, especially in light of our application of expressio unius in United States v. Kinard, 472 F.3d 1294, 1297-98 (11th Cir.2006), where we applied the principle in the context of federal sentence enhancement guidelines, restricting enhancement to the violation of one or more of the relevant enumerated statutes.
Additionally, reading “other criminal offenses” to include federal offenses, such as 18 U.S.C. § 1470, as suggested by the government, would turn the language “State, local, tribal, foreign, or [specified] military offense” into meaningless surplus-age thereby further complicating an attempt to provide a correct and coherent interpretation of the provision. For reasons given below, however, we do not need to decide this issue of statutory interpretation because, even if we assume that non-enumerated federal offenses, including violations of 18 U.S.C. § 1470, may qualify as “other criminal offenses,” Dodge still is not required to register.7
*1362The next step in our analysis comes in the application of subsection (7)(I) of section 16911. Subsection (7) provides an “expanded definition” of “specified crimes against a minor” with subsection (7)(I) being the only subsection (7) provision applicable to Dodge’s case. Subsection (7)(I) designates, as a “specified crime against a minor,” ... “[a]ny conduct that by its nature is a sex offense against a minor.” Dodge contends that the court should approach this definition in a “categorical” fashion such that only convictions under a statute for which all possible convictions would qualify as a “sex offense against a minor” would require registration. Accordingly, Dodge claims, the court should decline to examine the underlying behavior upon which his conviction is based, but rather determine only whether all convictions of 18 U.S.C. § 1470 would require registration. Thus, Dodge argues, a categorical approach would call only for a comparison of the fact of conviction and the definition of the offense of conviction on the one hand, and the definition set out in (7)(I) on the other.8 Because not all convictions of 18 U.S.C. § 1470 would require registration, under a categorical approach, no conviction under 18 U.S.C. § 1470 would require registration.
The government, on the other hand, encourages us to reject a categorical approach here, noting that the language in subsection (7)(I) calls for determining the “conduct” of the defendant in question, not the “conviction,” as was the case in Shepard. Id. Such a non-categorical approach was recently used by the 9th Circuit in United States v. Byun, 539 F.3d 982, 992 (9th Cir.2008),9 where that Court concluded that, “the best reading of the statutory structure and language is that Congress contemplated a non-categorical approach
Nonetheless, we do not have to decide whether or not to take a categorical approach to reading the statute. This is because even if we do not adopt a categorical approach requiring all violations of 18 U.S.C. § 1470 to be sex offenses against a minor in order to require registration, we still must be able to articulate a principled statutory basis for requiring registration for some violations of 18 U.S.C. § 1470 but not for others. Here, even if we agree with the government, and examine Dodge’s underlying conduct in this case, we are unable to distinguish Dodge’s conduct from conduct that would also support a conviction under 18 U.S.C. § 1470 but which would not require registration under SORNA because such conduct is not “by its nature a sex offense against a minor,” as required by subsection (7)(I).
Our inability to find a principled way to distinguish Dodge’s actions from *1363other actions that would also support a violation of 18 U.S.C. § 1470, but which clearly are not “by [their] nature a sex offense against a minor,” proceeds from a plain language reading of the statutory phrase “sex offense against.” Any definition of “against” requires a concept of contact or opposition. American Heritage Dictionary 32 (3d ed.1992). Dodge’s actions, offensive and deplorable though they may be, lack any element of an unwanted sexual assault, offense, or other violation that contacts or opposes a minor’s rights. Unlike a “flasher,” for example, there is no claim here that Dodge invaded the private space of a minor. While such an assault offense or other violation that contacts or opposes a minor’s rights may not be necessary elements of a crime which is “by its nature a sex offense against a minor,” it would provide a clear basis for concluding that the crime is a “sex offense against a minor,” and would, therefore, provide an acceptable or principled statutory rationale for imposition of SORNA’s registration requirement. Dodge’s actions, however, are not so distinguishable.
Violations of 18 U.S.C. § 1470 include the mere distribution of obscene material. For example, if Dodge, rather than sending photos and video of himself over the internet, had mailed the same materials or distributed hard-copy across state lines to people he knew to be under the age of sixteen, he would have equally violated 18 U.S.C. § 1470.10 These actions, however, would not be “by [their] nature a sex offense against a minor” because they do not involve an unwanted sexual assault or other violation against a minor’s rights. There is no principled way to distinguish Dodge’s conduct from these offenses that do not require registration. While both offenses violate an innocent party’s right not to have their inbox or mailbox invaded with obscene material, the activities are not clearly distinguishable in a way that would permit us to conclude that one is a “sex offense” while the other is not.
While we do not conclude that every violation of 18 U.S.C. § 1470 is exempt from SORNA’s registration requirement, because some such violations do not require registration, in order to require Dodge to register, we must be able to clearly distinguish his actions from other actions that would also support a conviction under 18 U.S.C. § 1470 but that are not “by [their] nature a sex offense against a minor.” Absent such a rationale, the registration requirements cannot be imposed. Accordingly, we conclude that the District Court erred in requiring Dodge to register as a Tier-1 Sex Offender under SORNA.11
As it is necessarily an abuse of discretion to base a ruling on an erroneous interpretation of a statute, Cooter & Gell v. Hartmarx Gorp., 496 U.S. 384, 405, 110 S.Ct. 2447, 110 L.Ed.2d 359 (1990), super-ceded on other grounds, Fed.R.Civ.P. 11, *1364we reverse the District Court’s ruling that Dodge must register under SORNA.
REVERSED.
. 18 U.S.C. § 1470 provides: "Whoever, using the mail or any facility or means of interstate or foreign commerce, knowingly transfers obscene matter to another individual who has not attained the age of 16 years, knowing that such other individual has not attained the age of 16 years, or attempts to do so, shall be fined under this title, imprisoned not more than 10 years, or both.”
. It is not relevant that, in all of the cases for which he was charged, Dodge apparently failed to interact with minors below the age of 16, but instead interacted with police officers or chat-room officials. This is because 18 U.S.C. § 1470 prohibits attempts to transfer obscene materials to a minor as well as actual transfers.
. The indictment also contained a fourth count, not at issue here, relating to forfeiture of Dodge's computer equipment.
. Subsections (5)-(7) of 42 U.S.C. § 16911 provide:
(5) Amie Zyla expansion of sex offense definition.
(A) Generally. Except as limited by sub-paragraph (B) or (C), the term "sex offense” means—
(i) a criminal offense that has an element involving a sexual act or sexual contact with another;
*1360(ii) a criminal offense that is a specified offense against a minor;
(iii) a Federal offense (including an offense prosecuted under section 1152 or 1153 of title 18, United States Code [18 USCS § 1152 or 1153]) under section 1591 [18 USCS § 1591], or chapter 109A [18 USCS §§ 2241 et seq.], 110 [18 USCS §§ 2251 et seq.] (other than section 2257, 2257A, or 2258 [18 USCS § 2257, 2257A, or 2258]), or 117 [18 USCS §§ 2421 et seq.], of title 18, United States Code;
(iv) a military offense specified by the Secretary of Defense under section 115(a)(8)(C)(i) of Public Law 105-119 (10 U.S.C. 951 note); or
(v) an attempt or conspiracy to commit an offense described in clauses (i) through (iv).
(6) Criminal offense. The term "criminal offense” means a State, local, tribal, foreign, or military offense (to the extent specified by the Secretary of Defense under section 115(a)(8)(C)(i) of Public Law 105-119 (10 U.S.C. 951 note)) or other criminal offense.
(7) Expansion of definition of "specified offense against a minor” to include all offenses by child predators. The term "specified offense against a minor” means an offense against a minor that involves any of the following:
(A) An offense (unless committed by a parent or guardian) involving kidnapping.
(B) An offense (unless committed by a parent or guardian) involving false imprisonment.
(C) Solicitation to engage in sexual conduct.
(D) Use in a sexual performance.
(E) Solicitation to practice prostitution.
(F) Video voyeurism as described in section 1801 of title 18, United States Code [18 USCS § 1801],
(G) Possession, production, or distribution of child pornography.
(H) Criminal sexual conduct involving a minor, or the use of the Internet to facilitate or attempt such conduct.
(I) Any conduct that by its nature is a sex offense against a minor.
. Plainly, a violation of 18 U.S.C. § 1470 is not one of the "Federal offense[s]” specified by Section 16911(5)(A)(III) as constituting a "sex offense.”
. The expressio unius canon is relevant to the interpretation of 42 U.S.C. § 1691 l(5)(iii) because all of the examples listed in that provision section are members of an associated group or series, i.e., they are types of federal offenses. Cf. Barnhart v. Peabody Coal Co., 537 U.S. 149, 168, 123 S.Ct. 748, 154 L.Ed.2d 653 (2003) ("the canon of expressio unius est exclusio alterius does not apply to every statutory listing or grouping; it has force only when the items expressed are members of an 'associated group or series,' justifying the inference that items not mentioned were eluded by deliberate choice, not inadvertence.”)
. While we do not decide the question of whether, as Dodge contends, non-enumerated federal crimes such as 18 U.S.C. § 1470 cannot fall into the category of "other crimes” without rendering the statute internally inconsistent or reducing language of "State, local, tribal, foreign, or [specified] military offense” to mere surplusage, we believe the mattér to be less straightforward than the reasoning our brother’s dissent would imply. For example, while "[njothing in the plain language of the statute suggests that 'other criminal offense' cannot encompass federal offenses not specifically enumerated in 42 U.S.C. § 1691 l(5)(A)(iii)” (Dissent at 1366), including unenumerated offenses would, as Dodge contends, render the statute inconsistent or reduce other language to mere surplusage. Consequently, the lack of a "plain language” restriction is beside the point. Similarly, invoking the "broad purpose and scope” of SORNA (id.) or legislative history (id. at 1366) cannot make the statute cover criminal offenses that would not otherwise be covered by the statute under the rule of law. In the words of Justice Scalia, "it is simply incompatible with democratic government, or indeed, even with fair government, to have the meaning of a law determined by what the lawgiver meant, rather than what the lawgiver promulgated.” Antonin Scalia, A Matter of Interpretation: Federal Courts and the law 17 (Princeton University Press 1997). A similar view, with regard to legislative history, was noted by Justice Jackson: "[w]hen we decide from legislative history, ... what Congress probably had in mind, we must put ourselves in the place of a majority of Congressmen and act according to the impression we think this history should have made on them .... That process seems to me not interpretation of a statute but creation of a statute.” United States v. Public Utils. Comm’n of Cal., 345 U.S. 295, 319, 73 S.Ct. 706, 97 L.Ed. 1020 (1953) (Jackson, J., concurring). Given that other well-established canons of interpretation weigh against the Dissent’s interpretation, notably the principle of expressio unius est exclusio alterius and the "rule of lenity” (see United States v. Bass, 404 U.S. 336, 347-49, 92 S.Ct. 515, 30 L.Ed.2d 488 (1971)), it seems that there is ground for doubt.
Similarly, the fact that 42 U.S.C. § 16911(7) includes "expansive language” *1362and lists other federal crimes does not unequivocally support the Dissent’s interpretation. Rather, the language of § 16911(7) suggests that Congress was perfectly capable of including other federal crimes via specific language, in a way that did not cause interpretive difficulty with the rest of the statute, when it wished to do so.
. Such a categorical approach has the advantage of allowing the sentencing (or reviewing) court to avoid the difficulty of having to conduct mini-trials on uncharged conduct. See, United States, v. Spell, 44 F.3d 936, 939 (11th Cir.1995). This approach was also favored by the Supreme Court in the context of enhancement guidelines in Shepard v. United States, 544 U.S. 13, 19-20, 125 S.Ct. 1254, 161 L.Ed.2d 205 (2005).
. In Byun, the Court determined that importation into the United States of an alien for purposes of prostitution constituted a sex offense against a minor where Byun's underlying conduct included transporting a minor with the intent that the minor engage in prostitution even though the age of the minor was not an element of the alien smuggling violation to which Byun plead guilty. Byun, 539 F.3d at 986-87, 993-94.
. The dissent would distinguish Dodge’s conduct from violations of 18 U.S.C. § 1470 that do not require registration on the basis that Dodge “intended for 13-year-old girls to view him in a sexual state.” Dissent at 1370. But violations of Section 1470 by mailing obscene material, even with the intent that a 13-year-old view the sender in a sexual state, would not require registration.
. The dissent would analogize Dodge’s conduct to conduct which violates 18 U.S.C. § 2252B(b). That statute criminalizes the use of a “misleading domain name on the Internet with the intent to deceive a minor into viewing material that is harmful to minors ....” Dissent at 1370. But 18 U.S.C. § 2252B(b) includes an element of predation or deception — the use of a "misleading domain name” not present under 18 U.S.C. § 1470.