Supreme Court denies New Mexico-Texas motion to resolve Rio Grande dispute without federal input

New Mexico and Texas cannot move forward with a deal aimed at resolving a decade-long dispute over Rio Grande River management, due to their failure to include the federal government in the process. 

The Supreme Court on Friday denied a motion made by the two states, along with neighboring Colorado, to enter a consent decree on the subject and instead sustained an exception made by the United States.

The consent decree had outlined how New Mexico and Texas would resolve past discrepancies as to how the former delivers water to the latter. But the U.S. maintained that their proposed agreement was both incompatible with a historic compact and would require the federal government to adhere to protocols that it hadn't approved.

"We agreed with the United States," Justice Ketanji Brown Jackson wrote in the opinion issued Friday morning.

"Although interstate compacts are (as the name suggests) agreements between States, 'we have sometimes permitted the federal government to participate in compact suits to defend "distinctively federal interests,"'" Jackson wrote, citing a 1981 Maryland v. Louisiana case as precedent.

The current case has roots in the 1938 Rio Grande Compact — an agreement that served to oversee river use in three U.S. states, through a debit-credit system that accounts for shifting hydrological conditions. Historically, New Mexico has obtained 57 percent of the domestic Rio Grande flow, while 43 percent has been sent to Texas.

The Rio Grande, which flows for 1,896 miles from its southwestern Colorado headwaters through New Mexico and Texas, also forms the U.S. border with Mexico and serves 20 tribal nations in New Mexico and two in Texas. As for Mexico, the U.S. signed a separate water-sharing agreement with its southern neighbor in 1906.

Jackson noted in the court's opinion on Friday that “the Compact is inextricably intertwined with the Rio Grande Project and the Downstream Contracts” — referring to contracts requiring the U.S. to facilitate water deliveries from New Mexico to Texas. By the time the compact was enacted, those contracts had already been negotiated, the opinion stressed.

If New Mexico, for example, interfered with water deliveries, the federal Bureau of Reclamation "might prove unable 'to meet its duties under the Downstream Contracts,'" Jackson continued. 

Regarding the U.S. commitment to Mexico, the opinion argued that “the United States’ ability to deliver water to Mexico depends on New Mexico’s compliance with ‘its Compact obligations.'" Any breach of the compact, the document explained, could undercut the government's ability to fulfill those duties.

"The United States has its own, uniquely federal claims under the Compact," Jackson stated. "If it did not, one might wonder why we permitted the Federal Government to intervene in the first place."