Page:Arizona v. Navajo Nation.pdf/10

Rh (1938); Winters v. United States, 207 U. S. 564, 576–577 (1908); see also Cappaert v. United States, 426 U. S. 128, 138–139 (1976). Each of those rights is a stick in the bundle of property rights that makes up a reservation.

This suit involves water. To help meet their water needs, the Navajos obtain water from, among other sources, rivers, tributaries, springs, lakes, and aquifers on the reservation. As relevant here, the Navajos do not contend that the United States has interfered with their access to water. Rather, the Navajos argue that the United States must take affirmative steps to secure water for the Tribe—for example, 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 Tribe asserts a breach-of-trust claim. 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 (2011); United States v. Navajo Nation, 537 U. S. 488, 506–507 (2003); United States v. Mitchell, 445 U. S. 535, 542, 546 (1980). The Federal Government owes judicially enforceable duties to a tribe “only to the extent it expressly accepts those responsibilities.” Jicarilla, 564 U. S., 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. Navajo Nation, 537 U. S., at 506. That requirement follows from separation of powers principles. As this Court recognized in Jicarilla, Congress and the President exercise the “sovereign function” of organizing and managing “the Indian trust relationship.” 564 U. S., at 175. So the federal courts in turn must adhere to the text of the relevant law—here, the treaty.