In the 1986 case Texas v. New Mexico, the U.S. Supreme Court was asked to resolve a dispute between these two states over water rights in relation to the Pecos River Compact of 1949. The compact had been designed to ensure that an equitable share of river water reached Texas from its source in New Mexico but did not specify how this should be achieved or measured. In this case, Texas claimed that it was receiving less than its fair share due to increased consumption and conservation measures by New Mexico upstream. The court appointed a Special Master who recommended that future deliveries be based on conditions as they existed at the time of signing (1947-1953), rather than current conditions which were affected by factors such as reservoir evaporation and groundwater pumping. The Supreme Court agreed with most recommendations made by the Special Master but rejected his proposal for measuring state-line flows during non-irrigation season, stating it would unfairly burden New Mexico without significantly benefiting Texas. This ruling clarified how compliance with interstate compacts is determined when specific measurement methods are not outlined within those agreements themselves.

In the dissenting opinion for Texas v. New Mexico, Justice Stevens argued that the majority's decision to allow New Mexico to divert water from the Pecos River was a violation of an interstate compact between Texas and New Mexico. He believed that this agreement should be honored as it had been in previous cases involving disputes over shared resources between states. Furthermore, he contended that by allowing one state to unilaterally alter its obligations under such a compact without mutual consent or negotiation would undermine future cooperative agreements between states. Additionally, he disagreed with the majority’s interpretation of “usable” water and stated it could lead to further disagreements down the line due to its ambiguity. Lastly, Justice Stevens expressed concern about how this ruling might affect other similar compacts across America.