Wind River Reservation Held Diminished: EPA’s Contrary Determination Set Aside Despite EPA Reliance on Solicitor Opinion

On February 22, 2017, the Tenth Circuit Court of Appeals issued a decision finding that the Wind River Reservation in Wyoming, established by, as relevant here, an 1896 treaty, was diminished by a 1905 Act of Congress in which the Eastern Shoshone and Northern Arapahoe Tribes (Tribes) which share the Reservation agreed to cede certain of their lands.1 The appeal came to the Tenth Circuit because the United States Environmental Protection Agency (EPA) had determined, in 2011, that the Tribes qualified to administer certain non-regulatory provisions of the Clean Air Act (CAA) on the Reservation.2  As part of the CAA application process, the Tribes were required to demonstrate jurisdiction, and the Tribes asserted jurisdiction over most of the land within the original 1868 boundaries of the Wind River Reservation.

In response to the Tribes’ application, Wyoming and others submitted comments to the EPA arguing that the Reservation had been diminished by the 1905 Act and, as a result, some of the land identified in the Tribes’ application was no longer under their jurisdiction. EPA disagreed, concluding that the Reservation had not been diminished, and granted the Tribes’ application. EPA relied, in part, on a Department of the Interior legal opinion concluding that the 1905 Act did not change the 1868 Reservation boundaries. Wyoming and the Wyoming Farm Bureau appealed to the Tenth Circuit.3

The Tenth Circuit relied on “well-settled approach described in Solem [v. Bartlett]”4 to analyze whether a subsequent congressional act, the 1905 Act, diminished the Reservation’s 1868 boundaries. The Solem approach is a three-step analytical framework. First, a court looks to the text of the statute that is purported to diminish or disestablish a reservation here, the 1905 Act. Second, a court examines the circumstances surrounding the passage of the relevant statute. Finally, the court looks, to a lesser extent, at “the subsequent treatment of the area in question and the pattern of settlement.”5

Language of the 1905 Act: The operative language of the 1905 Act provided that the Tribes, “for the consideration hereinafter named, do hereby cede, grant, and relinquish to the United States, all right, title and interest which they may have”6 to the land at issue. The language of the 1905 Act, according to the Tenth Circuit, “is nearly identical to the statutory language in cases where the Supreme Court has found a congressional purpose to diminishing a reservation.”7

Historical Context of the 1905 Act: The Tenth Circuit held that the circumstances surrounding the enactment of the 1905 Act confirmed Congress’ intent to diminish the Wind River Reservation. During the negotiations with the Tribes, the then-United States. Indian Inspector stated that the boundaries of the reservation would change and cession of the lands to the United States would leave a “diminished reservation.”8 Statements made by tribal representatives during the negotiations reflected the Tribes’ understanding that the Reservation would be diminished. The Court noted that the legislative history and negotiations leading to the 1905 Act’s passage evidenced Congress’ intent to sever part of the original reservation and exclude it from the continuing reservation.

Subsequent Treatment of the Area: The Court first noted that the parties had supplied volumes of materials supporting their respective positions from which the Court was “unable to discern clear congressional intent.”9 The Court thus found, consistent with Solem, the materials regarding subsequent treatment of the area had “little evidentiary value.”10 The Court nevertheless reviewed the most germane material and concluded that it supported a finding of diminishment.

Judge Lucero’s Dissent: Judge Lucero dissented from the majority opinion, primarily based on his reading of the 1905 Act, which, as the majority conceded contains no language providing for a sum certain payment to the Tribes, nor did it contain language restoring the lands to the public domain. Rather than providing for sum certain payment, the 1905 Act provided that the United States would act as the Tribes’ trustee and pay to the Tribes the proceeds received from the sale of the ceded lands. According to Judge Lucero, the majority’s reliance on cases that analyzed acts containing “sum certain” language was misplaced. Judge Lucero analogized the 1905 Act to language at issue in Ash Sheep Co. v. United States,11 a 1920 Supreme Court decision in which the Supreme Court held that the release of the possessory interest in the tribes’ land did not diminish the tribes’ reservation, and those lands remained Indian lands because the benefits of those lands belonged to the Indians until the lands were sold. Judge Lucero analyzed the 1905 Act as not diminishing the Reservation, but simply providing for the sale and opening of lands. Judge Lucero found the historical context of the 1905 Act to be mixed regarding Congress’ intent and insufficient to overcome what he considered ambiguous language in the 1905 Act.

Take-Away: Wind River demonstrates that the era in which reservation diminishment issues may arise is not over. It is interesting, however, that the Tenth Circuit did not defer to the Department of the Interior Solicitor’s legal opinion concluding that the 1905 Act did not diminish the Reservation boundaries, given that such a legal opinion would be within the Department of the Interior’s expertise. The Tenth Circuit cites the Solicitor’s opinion in several places in the Wind River decision, but only discusses the opinion’s conclusions with respect to the Solicitor’s findings under the third prong, subsequent treatment of the area. The Solicitor opinion concluded that evidence after 1905 “indicates some inconsistent treatment of the 1905 area.” The Solicitor opinion also concluded that the maps referencing the ceded lands as “open lands” were “ambiguous and inconsistent at best.”  The Tenth Circuit ultimately concluded that the evidence of the subsequent treatment of the land neither bolstered nor undermined the Court’s diminishment decision. The Tenth Circuit also did not defer to the EPA, which is not entirely surprising, given that the EPA has no special expertise in ascertaining whether a reservation has been diminished.  


1 Wyoming v. Envtl. Prot. Agency, Nos. 14-9512 & 9514, 2017 U.S. App. LEXIS 3120 (Feb. 22. 2017).

2 In 1990, Congress amended the Clean Air Act to allow the EPA to treat tribes as states for purposes of the Act. This authority is known as “treatment as state” status or TAS.

3 See 42 U.S.C. § 7607(b)(1).

4 465 U.S. 463 (1984).

5 Wyoming, No. 14-9512, at *12 (quoting South Dakota v. Yankton Sioux Tribe, 522 U.S. 329, 344 (1998)).

6 Id. at *13 (emphasis in original) (quoting 1905 Act, 33 Stat. at 1016).

7 Id. at *14.

8 Id. at *27 (emphasis in original).

9 Id. at *34.

10 Id.

11 Ash Sheep Co. v. United States, 252 U.S. 159 (1920).


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