The U.S. Supreme Court case Wyoming v. Colorado in 1939 was a dispute over water rights between the two states, specifically concerning the Laramie River. The court ruled that Colorado had to limit its use of water from the river so as not to interfere with Wyoming's prior appropriation rights under an interstate compact agreement signed by both states and approved by Congress in 1922. This decision upheld principles of equitable apportionment, which means that when there is a conflict over shared resources such as water or land, courts will try to divide them fairly among all parties involved based on their respective needs and uses rather than strictly adhering to state boundaries or property lines.

In the dissenting opinion for Wyoming v. Colorado, it was argued that the Supreme Court should not have jurisdiction over this case as it is essentially a dispute between two states about water rights and allocation from an interstate river. The dissenting justices believed that such matters should be resolved through negotiation and agreement between the involved states rather than by judicial decision. They also expressed concern about setting a precedent where federal courts would become arbiters in state disputes over natural resources, which could potentially lead to numerous similar cases flooding the court system. Furthermore, they disagreed with majority's interpretation of "equitable apportionment," arguing instead that priority of appropriation should play a more significant role in determining water rights among western states where water scarcity is common.