Texas v. New Mexico

Background

Texas sued New Mexico and Colorado in this Court over how water from the Rio Grande is shared. The Rio Grande Compact, approved by Congress, requires Colorado to send water to New Mexico and requires New Mexico to deliver water to the Elephant Butte Reservoir. Separate Downstream Contracts promise reservoir water to New Mexico and Texas water districts, and the United States has a treaty duty to deliver water to Mexico. Texas says New Mexico allowed downstream users to take water below the reservoir in ways that violate the Compact. The United States intervened and filed a complaint that largely mirrors Texas’s claims.

Reasoning

The central question was whether the federal government, after joining Texas’s suit, may press Compact-based claims. The Court said yes. It explained that original cases between States give the Court flexibility to shape who may participate. The Justices relied on four points: the Compact is closely tied to the federal Rio Grande Project and the Downstream Contracts; New Mexico conceded the United States plays an integral operational role; a Compact breach could harm the United States’ ability to meet its treaty duty to Mexico; and the United States pressed the same relief alongside Texas without Texas objecting. The Court sustained the United States’ exception and remanded the case for further proceedings.

Real world impact

The ruling allows the federal government to press Compact claims here to help ensure reservoir operations and treaty water deliveries. It does not decide whether the United States could start such a case on its own or expand the dispute; the underlying water-rights issues remain for later proceedings.