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Rh Navajo may have in the river. Id., at 110. The Department posited that figuring that out would be a “somewhat lengthy process,” one that had “yet to be initiated.” Ibid.

Unwilling to wait indefinitely, the Navajo eventually filed this suit. In it, the Navajo sought “injunctive and declaratory relief to compel the Federal Defendants to determine the water required to meet the needs of the Nation’s lands in Arizona and devise a plan to meet those needs to fulfill the promise of the United States to make the Nation’s Reservation lands a permanent homeland for the Navajo people.” Id., at 86. In other words, the Tribe asked the United States to assess what water rights it holds in trust on the Tribe’s behalf pursuant to the Treaty of 1868. Tr. of Oral Arg. 71–72. And if it turns out the United States has misappropriated those water rights, the Tribe wants the federal government to come up with a plan to set things right.

With a view of this history, the proper outcome of today’s case follows directly. The Treaty of 1868 promises the Navajo a “permanent home.” Treaty Between the United States of America and the Navajo Tribe of Indians, June 1, 1868, Art. XIII, 15 Stat. 671 (ratified Aug. 12, 1868) (Treaty of 1868). That promise—read in conjunction with other provisions in the Treaty, the history surrounding its enactment, and background principles of Indian law—secures for the Navajo some measure of water rights. Yet even today the extent of those water rights remains unadjudicated and therefore unknown. What is known is that the United States holds some of the Tribe’s water rights in trust. And it exercises control over many possible sources of water in which the Tribe may have rights, including the mainstream of the Colorado River. Accordingly, the government owes the Tribe a duty to manage the water it holds for the Tribe in a legally responsible manner. In this lawsuit, the Navajo