In the 1982 case of Arizona v. California et al., the Supreme Court was tasked with resolving a dispute over water rights to the Colorado River between several Western states and Native American tribes. The court had previously allocated specific amounts of river water to each state in a 1963 decision, but this allocation did not account for federal Indian reservations established along the river's banks. In its ruling, the court held that five Indian reservations were legally entitled to enough water from the main stream of the Colorado River to irrigate all practicably irrigable acreage on their lands. This effectively increased Arizona’s share as it hosted most of these reservations within its borders. Furthermore, it ruled that United States as trustee for reservation Indians could claim future mainstream water rights when necessary to fulfill purposes of affected Indian Reservations even if such claims would disrupt allocations made among Lower Basin States (California, Nevada and Arizona). The decision significantly impacted western water law by recognizing tribal reserved rights as having priority over other uses under state law.

In the dissenting opinion for Arizona v. California et al., 1982, it was argued that the Supreme Court had overstepped its jurisdiction by ruling on a matter of state water rights without sufficient evidence or expertise. The dissenters believed that the case should have been remanded to a Special Master for further fact-finding and consideration of complex issues related to water allocation in the Colorado River Basin. They felt that this would have allowed for more thorough examination and understanding of relevant factors such as population growth, changes in agricultural practices, climate change impacts, and evolving legal doctrines around water use rights. Furthermore, they disagreed with majority's interpretation of Boulder Canyon Project Act (BCPA) which led them to uphold Secretary’s apportionment among lower basin states without considering other potential equitable apportionments under federal law or interstate compacts.