This post was originally published by SCOTUSblog. Reprinted under Creative Commons license CC-BY-NC-ND 3.0.

The Supreme Court on Tuesday unanimously struck down a Washington state law that was aimed at helping federal contract employees get workers' compensation for diseases arising from cleaning up nuclear waste.

The case, United States v. Washington, concerned the federally controlled Hanford nuclear reservation, a decommissioned facility that spans 586 square miles near the Columbia River. The reservation, formerly used by the federal government in the production of nuclear weapons, presents unique hazards to cleanup workers.

Under longstanding law, the federal government is immune from application of state law, including liability rules, on federal property located within a state, unless Congress waives the immunity. As Justice Stephen Breyer explained at the outset of his opinion for the court: "The Constitution's Supremacy Clause generally immunizes the Federal Government from state laws that directly regulate or discriminate against it." This concept is popularly known as "intergovernmental immunity."

Intergovernmental immunity might have meant that nonfederal workers on the Hanford site would automatically have no access to state remedies for work-related injuries or diseases. In 1936, however, Congress, detecting state workers' compensation gaps in injury coverage of …