Syllabus

NOTE: Where it is feasible, a syllabus (headnote) will be released, as is being done in connection with this case, at the time the opinion is issued. The syllabus constitutes no part of the opinion of the Court but has been prepared by the Reporter of Decisions for the convenience of the reader. See United States v. Detroit Timber & Lumber Co., 200 U. S. 321, 337.

SUPREME COURT OF THE UNITED STATES

Syllabus

ARIZONA ET AL. v. NAVAJO NATION ET AL. CERTIORARI TO THE UNITED STATES COURT OF APPEALS FOR THE NINTH CIRCUIT

No. 21–1484. Argued March 20, 2023—Decided June 22, 2023* An 1868 peace treaty between the United States and the Navajo Tribe established the Navajo Reservation that today spans some 17 million acres, almost entirely in the Colorado River Basin of the western United States. The Federal Government’s reservation of land for an Indian tribe implicitly reserves the right to use needed water from var- ious sources—such as groundwater, rivers, streams, lakes, and springs—that arise on, border, cross, underlie, or are encompassed within the reservation. See Winters v. United States, 207 U. S. 564, 576–577. While the Tribe has the right to use needed water from the reservation’s numerous water sources, the Navajos face the same wa- ter scarcity problem that many in the western United States face. In the Navajos’ view, the Federal Government’s efforts to assist the Nav- ajos with their water needs did not fully satisfy the trust obligations of the United States under the 1868 treaty. The Navajos filed suit seek- ing to compel the United States to take affirmative steps to secure needed water for the Tribe—including by assessing the Tribe’s water needs, developing a plan to secure the needed water, and potentially building pipelines, pumps, wells, or other water infrastructure. The States of Arizona, Nevada, and Colorado intervened against the Tribe to protect those States’ interests in water from the Colorado River. The U. S. District Court for the District of Arizona dismissed the Navajo Tribe’s complaint, but the Ninth Circuit reversed, holding in relevant part that the United States has a duty under the 1868 treaty to take affirmative steps to secure water for the Navajos. —————— * Together with No. 22–51, Department of the Interior et al. v. Navajo Nation et al., also on certiorari to the same court. 2 ARIZONA v. NAVAJO NATION

Syllabus Held: The 1868 treaty establishing the Navajo Reservation reserved nec- essary water to accomplish the purpose of the Navajo Reservation but did not require the United States to take affirmative steps to secure water for the Tribe. Pp. 6–13. (a) The Tribe asserts a breach-of-trust claim based on its view that the 1868 treaty imposed a duty on the United States to take affirma- tive steps to secure water for the Navajos. To maintain such a claim here, the Tribe must establish, among other things, that the text of a treaty, statute, or regulation imposed certain duties on the United States. See United States v. Jicarilla Apache Nation, 564 U. S. 162, 173–174, 177–178. The Federal Government owes judicially enforcea- ble duties to a tribe “only to the extent it expressly accepts those re- sponsibilities.” Id., at 177. Whether the Government has expressly accepted such obligations “must train on specific rights-creating or duty-imposing” language in a treaty, statute, or regulation. United States v. Navajo Nation, 537 U. S. 488, 506. Here, while the 1868 treaty “set apart” a reservation for the “use and occupation of the Navajo tribe,” 15 Stat. 668, it contains no language imposing a duty on the United States to take affirmative steps to se- cure water for the Tribe. See Navajo Nation, 537 U. S., at 506. Nota- bly, the 1868 treaty did impos