What is the supremacy clause?
Answer
The clause stating the Constitution is the supreme law of the land
Explanation
The Supremacy Clause is the provision in Article VI, Clause 2 of the Constitution that declares the Constitution, federal laws made under it, and treaties of the United States to be the supreme law of the land, binding on every judge in every state, anything in state constitutions or laws to the contrary notwithstanding. The clause solves a problem that had crippled the Articles of Confederation between 1781 and 1789, when state laws could override national policy and there was no clear hierarchy of legal authority. Without supremacy, federal taxes could be ignored, federal court orders refused, and treaties violated by individual states. The Founders, after watching the union nearly collapse under such weakness, wrote the Supremacy Clause specifically to ensure that valid federal law trumps conflicting state law.
The clause has three parts. First, the Constitution itself sits at the top of the legal hierarchy. Second, federal statutes that fall within Congress's enumerated powers are also supreme over state law. Third, treaties made under the authority of the United States have the force of supreme law as well. State constitutions, state statutes, state regulations, and state court decisions cannot override these federal sources.
The clause has been at the center of major Supreme Court rulings. McCulloch v. Maryland in 1819 used it to strike down a Maryland tax on the Bank of the United States. Cooper v. Aaron in 1958 enforced the Court's school desegregation rulings against Arkansas, asserting that the federal Constitution and federal court interpretations of it bind state officials. Arizona v. United States in 2012 used the clause to strike down parts of a state immigration law that conflicted with federal policy.
The clause also provides the doctrinal basis for federal preemption, where a federal statute is held to preempt or displace a state law dealing with the same subject. Preemption can be express, when a federal law explicitly says so, or implied, when federal regulation is so comprehensive that no room remains for state action.
The clause does not give the federal government unlimited authority. It only makes federal law supreme within its constitutional limits. State law continues to govern in vast areas not preempted by federal action.
Why this matters for your test
Understanding the Supremacy Clause explains why a single federal statute or Supreme Court ruling can override a contrary law in any of the fifty states, why a federal court can order a governor to comply with constitutional requirements, and why international treaties carry the same weight as federal statutes. It is what holds a federal system of fifty states together as one nation.
Source: USCIS 128 Civics Questions (2025)
