What is the Full Faith and Credit Clause?

The Full Faith and Credit Clause is Article IV, Section 1 of the Constitution: "Full Faith and Credit shall be given in each State to the public Acts, Records, and judicial Proceedings of every other State. And the Congress may by general Laws prescribe the Manner in which such Acts, Records and Proceedings shall be proved, and the Effect thereof." In practice, it means a valid court judgment, a marriage or divorce decree, or a public record issued in one state must generally be recognized and enforced by every other state, even if that state's own law might have reached a different result. The Supreme Court explained the clause's purpose in Allstate Insurance Co. v. Hague (1981) as being to "transform the several States from independent sovereignties into a single, unified Nation" - the clause is fundamentally about horizontal federalism, governing how the states relate to one another rather than how they relate to the federal government. A practical example: if a court in one state issues a valid civil judgment against a defendant, the winning party can take that judgment to any other state and have it enforced there directly, without relitigating the underlying facts of the case - the second state's courts generally cannot second-guess whether the first court got the merits right, only whether it had proper jurisdiction. The clause is not absolute; it has recognized limits, most notably a state's own strong public policy can, in narrow circumstances, allow it to decline to apply another state's law to a dispute even while still enforcing that state's judgments. Congress also has explicit constitutional authority under the clause's second sentence to pass laws governing exactly how the recognition process works, which it has used at various points, including in disputes over interstate recognition of certain civil judgments. Without this clause, the United States would function much closer to a loose confederation of fifty separate legal systems, each free to ignore the others' courts and records - the clause is one of the structural mechanisms that makes national legal coherence possible.