Arizona v. California

Background

Arizona asked to file a lawsuit asking a federal court to fix how much of the Colorado River each state may use, and to limit California’s share based on federal and state rules. The State said it needs water to irrigate millions of acres and that pending California projects and contracts threaten Arizona’s future ability to secure water for large-scale irrigation. The petition was filed against several Western states and described federal dams, contracts, and large planned diversions for California corporations.

Reasoning

The central question was whether the Court could decide how to divide the unclaimed (unappropriated) river water when the United States has already built dams, entered contracts, and claims authority under federal law. The Court held it could not. The opinion explains that the United States, through Congress and the Secretary of the Interior, controls storage and delivery of the river’s impounded water under the Boulder Canyon Project Act and related contracts. Because federal authority and contracts are central to who may use the stored water, the United States is an indispensable party and cannot be bound by a decree in its absence. For that reason the Court denied Arizona’s request to file the suit.

Real world impact

The decision leaves immediate, final allocation of the unappropriated Colorado River water unresolved. Arizona cannot obtain the requested nationwide division without the United States as a party. Arizona remains free to pursue claims in proceedings that include the federal government or otherwise challenge federal or state actions that it believes exceed lawful authority.