concurring:
I concur in the majority’s ultimate holding. I write separately because I believe that the term “authorized” is considerably more ambiguous than the majority opinion allows and that reliance on the deference due to the Secretary’s interpretation of the Flathead Act is a sounder ground for affirming.
The majority is quite correct that the term “authorized” may be interpreted as connoting a delegation not only of power or authority, but also of discretion. There is, however, another, equally acceptable definition of the term. Webster’s Third New International Dictionary defines the term simply to mean: “to give legality or effective legal force to.” Webster’s Third New International Dictionary 146 (1986). This alternative understanding of the term is reflected in the Black’s Law Dictionary definition published contemporaneously with passage of the Flathead Act: “ ‘Authorized’ is sometimes construed as equivalent to ‘permitted’; and sometimes as equivalent to ‘directed’; or to similar mandatory language.” Black’s Law Dictionary 169 (4th ed.l968)(internal citations omitted). To illustrate the directed or mandatory use of the term “authorized”, the 1968 edition of Black’s Law Dictionary cites two cases, neither of which interpreted statutes that contained additional words or terms expressing mandatory intent. See U.S. Sugar Equalization Board v. P. De Ronde & Co., 7 F.2d 981, 986 (3d Cir.1925); Catron v. Marron, 19 N.M. 200, 142 P. 380, 382 (1914); see also 3 Sutherland Statutory Construction 46 (6th ed. 2001)(“Where statutes provide for performance of acts or the exercise of power or authority by public officers protecting private rights or the public interest, they are mandatory.”).
Nor does Congress’ use of the word “shall” in § 2 of the Flathead Act indicate that the term “authorized” in the same section is permissive. If “authorized” is given a mandatory meaning in the first sentence of § 2, then there is no conflict with the mandatory term “shall” in the second sentence. See In re Thrift Shoe Co., Inc., 502 F.2d 1211, 1213(9th Cir.1974).
Although I am not convinced that the plain language of the statute allows no other construction, I believe that the Secretary’s construction of § 2 of the Flathead Act is reasonable and entitled to Chevron deference.1 The Senate Report *1198on the Flathead Act indicates that Congress wanted the Secretary to retain discretion over Flathead Act transfers. S.Rep. No. 1134, at 2 (1968) (“The purpose of [the Act] ... is to authorize the disposal of [land on the Flathead Reservation], and to authorize the Tribes to acquire Indian- or non-Indian-owned lands to be held in trust for tribal use or conveyance to tribal members in trust. Any transfer of lands under the bill would be subject to the prior approval of the Secretary of the Interi- or. ”)(emphasis added).
The Secretary’s construction of the Flathead Act is also consistent with the earlier, more general Indian Reorganization Act of 1934 (“IRA”). The IRA provides that, “[t]he Secretary of the Interior is hereby authorized, in his discretion, to acquire ... any interest in lands ... within or without existing reservations....” 25 U.S.C. § 465. The Tribes, citing Muscogee Nation v. Hodel, 851 F.2d 1439, 1443-44(D.C.Cir.1988), argue the omission of the term “in his discretion” from the later Flathead Act indicates that Congress intended to change the Secretary’s authority from discretionary to mandatory in enacting the Flathead Act. It is, however, equally likely that the omission of these words from § 2 of the Flathead Act was intended to indicate that authority to acquire lands could now be triggered by the Tribes’ request, rather than solely by the Secretary’s independent decision to acquire lands for the Tribes.
The Tribes argue that this Court must interpret any ambiguities in the Flathead Act in their favor under Montana v. Blackfeet Tribe, 471 U.S. 759, 766, 105 S.Ct. 2399, 85 L.Ed.2d 753 (1985). In Blackfeet Tribe, the Supreme Court stated that “statutes are to be construed liberally in favor of the Indians, with ambiguous provisions interpreted to their benefit.” Id. However, this Court has held that the canon of liberal interpretation in favor of Native Americans must give way to the Chevron rule that deference be accorded to an agency’s reasonable interpretation of a statute. Williams v. Babbitt, 115 F.3d 657, 663 n. 5 (9th Cir.1997)(citing Shields v. United States, 698 F.2d 987, 991 (9th Cir.1983)). Thus, the Secretary’s reasonable interpretation of § 2 of the Flathead Act must be given deference.
. The Tribes contend that the Secretary's interpretation of the Flathead Act conflicts with prior interpretations by the Department of Interior contained in a 1968 memorandum from the Billings Field Solicitor and a 1972 memorandum from the Billings Area Director. Even assuming that these memoran-da represent an interpretation by the Department of the Interior, they do not support the Tribes' position. Both memoranda offer a construction of the Flathead Act that is wholly consistent with that adopted by both the IBIA and the district court. The 1972 memoranda even states that, "[t]he word shall' as used in Section 1 is mandatory, while the word 'authorized' as employed in Section 2 is permissive.” Furthermore, an administrative agency "is not precluded from announcing new *1198principles in an adjudicative proceeding and ... the choice between rulemaking and adjudication lies in the first instance within the agency's discretion.” NLRB v. Bell Aerospace Co., 416 U.S. 267, 294, 94 S.Ct. 1757, 40 L.Ed.2d 134 (1974).