In the United States v. Arizona case of 1934, the Supreme Court ruled on a dispute over water rights between California and Arizona in relation to the Colorado River. The court held that Congress had complete control over interstate commerce and thus could regulate navigation on interstate waterways, including allocation of water resources from such bodies. This decision was based on Article I, Section 8 of the U.S Constitution which gives Congress power to regulate Commerce with foreign Nations, among several states and with Indian Tribes. Therefore, it was within its jurisdiction to approve or disapprove projects like Boulder Dam (now Hoover Dam) without consulting affected states or obtaining their consent. The ruling essentially reinforced federal supremacy over state laws in matters concerning interstate commerce.

The dissenting opinion in the United States v. Arizona case of 1934 argued that the federal government did not have exclusive jurisdiction over submerged lands and waters within a state's boundaries, contrary to what the majority held. The dissenters believed that when Arizona became a state, it gained sovereign rights over these areas just like any other state. They contended that nothing in the Constitution or laws of Congress deprived states of this right upon admission to Union. Furthermore, they pointed out inconsistencies with previous court decisions which had recognized such rights for original states but denied them for newer ones like Arizona. In their view, all states should be treated equally regardless of when they joined Union and thus possess equal sovereignty under law including control over their navigable waters and underlying soils.