In the case of Arizona v. California et al., 1962, the Supreme Court was tasked with resolving a dispute over water rights to the Colorado River between several western states and Mexico. The court ruled in favor of California, determining that it had rights to 4.4 million acre-feet per year from the mainstream waters of the river, while Arizona was entitled to 2.8 million acre-feet per year and Nevada received only 300 thousand acre-feet annually. This decision also recognized that Indian reservations along this river were entitled to significant portions of these state allocations for their own use under federal law - an important recognition for Native American tribes' sovereignty and resource access rights within U.S borders.

In the dissenting opinion for Arizona v. California et al., Justice Harlan disagreed with the majority's decision to allow a special master to determine water rights between states without first having Congress clarify its intent regarding the Boulder Canyon Project Act of 1928. He argued that this act was ambiguous and needed Congressional clarification before any legal interpretation could be made. Furthermore, he believed that it was not within the Supreme Court’s jurisdiction to interpret or decide on matters related to political questions such as interstate disputes over resources, which should instead be resolved by Congress through legislation. Therefore, in his view, allowing a special master to make these determinations would violate separation of powers principles and potentially lead to unjust results due to lack of clear legislative guidance.