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.
Article IV, Section 1 ensures that states respect and honor the state laws and court orders of other states, even when their own laws are different. For example, if citizens of New Jersey marry, divorce, or adopt children in New Jersey, Florida must recognize these actions as valid even if the marriage or divorce would not have been possible under Florida law. Similarly, if a court in one state orders a person to pay money or to stop a certain behavior, the courts in other states must recognize and enforce that state’s order.
Article IV, Section 1 also gives Congress the power to determine how states recognize records and laws from other states and how they enforce each others’ court orders. For example, Congress may pass a federal law that specifies how states must handle child custody disputes when state laws are different or that sets out the process by which a person winning a lawsuit in one state can enforce the order in another state.