## Facts

- Colorado, New Mexico, and Texas entered the Rio Grande Compact of 1938, later approved by Congress, to allocate and manage Rio Grande Basin water deliveries among the states.
- The United States, through the Bureau of Reclamation, operates the Rio Grande Project, including Elephant Butte Reservoir, and releases stored water for downstream uses.
- Federal “downstream contracts” require the United States to deliver water from Project storage to irrigation districts in southern New Mexico and western Texas.
- The United States also must deliver 60,000 acre-feet of water annually to Mexico at Ciudad Juárez under the 1906 Convention between the United States and Mexico.
- Texas filed an original action in the Supreme Court against New Mexico and Colorado, alleging New Mexico violated the Compact by allowing diversions and groundwater pumping below Elephant Butte that reduced deliveries Texas claimed were due under the Compact.
- The United States moved to intervene and filed a complaint asserting that New Mexico’s conduct also violated the Compact and interfered with federal project operations, federal contractual delivery duties, and treaty deliveries to Mexico.
- A Special Master recommended dismissing the United States’ complaint to the extent it asserted Compact-based claims, reasoning that the Compact was an agreement among states and did not give the United States authority to enforce its terms.
- The United States and Colorado filed exceptions, presenting the question whether the United States could pursue Compact-violation claims in this original action (and whether it should be confined to treaty-based claims only).

## Issues

1. Whether the United States may intervene in this original action and pursue the Compact-violation claims it pleaded.
2. Whether the United States must be limited to claims tied only to its 1906 treaty obligation to Mexico, rather than Compact-based claims.

## Decision

- The Court unanimously rejected the Special Master’s recommendation to bar the United States’ Compact claims.
- The Court held that the United States may intervene and pursue the Compact-violation claims it pleaded in this original action.
- The Court declined to limit the United States to treaty-only claims, concluding that federal interests related to the Rio Grande Project and downstream contracts are also at stake and are closely connected to the Compact’s operation.
- The Court treated the ruling as procedural and party-structuring in nature: it allowed the case to proceed with the United States asserting Compact claims, without deciding the merits of Texas’s or the United States’ allegations that New Mexico violated the Compact.

## Legal Principles

- A congressionally approved interstate compact functions as federal law, and disputes over its performance can involve federal interests beyond those of the signatory states.
- In an original action, the Supreme Court has special discretion to structure the litigation to support a fair and effective resolution, including deciding which parties and claims may be included.
- The United States may be permitted to litigate Compact-based claims in an interstate compact dispute when it shows federal interests that are not merely a restatement of a state’s allocation claim—such as interests tied to operation of a federal reclamation project, performance of federal water-delivery contracts, and compliance with an international treaty.
- Allowing the United States to press Compact claims in this case does not resolve whether the United States could start Compact-enforcement litigation on its own in a different setting, nor does it decide the underlying Compact-violation allegations.

## Conclusion

Texas v. New Mexico allowed the United States to intervene in the Rio Grande Compact original action and to pursue Compact-violation claims because the Compact’s operation is bound up with the federal Rio Grande Project, federal downstream delivery contracts, and the United States’ treaty duty to deliver water to Mexico; the Court therefore kept the federal government in the case to litigate those Compact-based claims while leaving the merits for later proceedings.


Texas v. New Mexico, 583 U.S. 401 (2018)