The United States (plaintiff) had an interest in the Rio Grande, including a treaty with Mexico to deliver 60,000 acre-feet of water annually via water stored in the Elephant Butte reservoir (the reservoir) in New Mexico. The United States also created and managed multiple water projects that participated in the delivery of water to Colorado (defendant), New Mexico (defendant), and Texas (defendant), including the reservoir and the dam that created the reservoir. Colorado, New Mexico, and Texas had competing interests in the waters of the Rio Grande. The three states, therefore, entered into several agreements, the most relevant of which was the Rio Grande Compact (the compact). Under the Compact Clause of the United States Constitution, as an agreement between states, the compact had to be, and was, approved by Congress and became federal law. Texas brought an action against New Mexico (and nominally Colorado) in the United States Supreme Court under the court’s original jurisdiction, claiming that New Mexico was not delivering water to the reservoir and therefore had breached the compact. The United States intervened in Texas’s action and brought its own complaint, essentially seeking the same breach-of-compact claim against New Mexico as asserted by Texas. The Supreme Court appointed a special master to assist with the cases. As a preliminary matter, New Mexico moved to dismiss the United States’ complaint, arguing that the United States had no power to enforce the compact between the states. The special master recommended dismissing the United States’ claim, and the United States and Colorado objected. The question before the Supreme Court was the scope of claims the United States could assert in its separate action.