United States v. Locke, 529 U.S. 89 (2000)
U.S. v.
Does the State of Washington's regulation of oil tankers within its waters conflict with, and therefore be preempted by, federal maritime regulations under the Supremacy Clause?
Under the Supremacy Clause, federal law preempts state law when Congress explicitly or implicitly indicates intent to occupy a regulatory field completely, when state law conflicts with federal law, or when state law poses an obstacle to the accomplishment of federal objectives.
The U.S. Supreme Court held that Washington State's regulations were preempted by federal law. The Court invalidated certain state regulations, emphasizing that federal maritime laws occupy the field of maritime regulation, thereby precluding states from imposing additional regulations.
U.S. v. Locke is significant for law students as it underscores the doctrine of federal preemption, especially in fields requiring uniform regulatory standards like maritime commerce. It serves as a critical example of the boundaries of state regulatory authority in contexts that have nationwide and international implications. The case is instrumental in demonstrating how the judiciary interprets congressional intent to either occupy a regulatory field completely or allow space for state-level experimentation.