Opinion of the Court
sought to “compel the Federal Defendants to determine the water required to meet the needs” of the Navajos in Arizona and to “devise a plan to meet those needs.” App. 86. The States of Arizona, Nevada, and Colorado intervened against the Tribe to protect those States’ interests in water from the Colorado River.
According to the Navajos, the United States must do more than simply not interfere with the reserved water rights. The Tribe argues that the United States also must take affirmative steps to secure 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. See Tr. of Oral Arg. 102 (counsel for Navajo Nation: “I can’t say that” the United States’s obligation “to ensure access” to water “would never require any infrastructure whatsoever”).
The U. S. District Court for the District of Arizona dismissed the Navajo Tribe’s complaint. In relevant part, the District Court determined that the 1868 treaty did not impose a duty on the United States to take affirmative steps to secure water for the Tribe.
The U. S. Court of Appeals for 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. Navajo Nation v. United States Dept. of Interior, 26 F. 4th 794, 809–814 (2022). This Court granted certiorari. 598 U. S. ___ (2022).
II
When the United States establishes a tribal reservation, the reservation generally includes (among other things) the land, the minerals below the land’s surface, the timber on the land, and the right to use needed water on the reservation, referred to as reserved water rights. See United States v. Shoshone Tribe, 304 U. S. 111, 116–118
