Glossary

Supremacy Clause

The Article VI provision making the Constitution, federal laws and treaties the supreme law of the land over conflicting state law.

Also called: Article VI supremacy, federal preemption

The Supremacy Clause, in Article VI of the Constitution, declares that the Constitution, federal laws made under it and treaties are "the supreme Law of the Land," and that state judges are bound by them regardless of anything in state constitutions or laws.

The clause is the source of the doctrine of preemption. Federal law can preempt state law expressly, when Congress says so; by occupying an entire field of regulation; or by conflict, when obeying both laws is impossible or the state law obstructs federal goals. Arizona v. United States (2012), for example, struck down parts of an Arizona immigration law as preempted by federal immigration statutes.

The clause makes federal law supreme only when it is valid, meaning within the federal government's enumerated powers. That limit is why it coexists with the Tenth Amendment and the anti-commandeering doctrine. Disputes over marijuana legalization, gun regulation, immigration enforcement and sanctuary jurisdiction policies all turn on where federal supremacy ends and state authority under federalism begins.

Last reviewed November 8, 2026

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Related terms

Federalism A system dividing governing power between a national government and state governments, each with its own sphere of authority. Tenth Amendment The amendment confirming that powers not delegated to the federal government are reserved to the states or to the people. Sanctuary jurisdiction A state or local government that limits its cooperation with federal immigration enforcement, often by declining to honor detainer requests. Enumerated powers The specific powers the Constitution grants to Congress and the federal government, chiefly the list in Article I, Section 8.