Full Faith and Credit Clause
The Full Faith and Credit Clause of the U.S. Constitution ensures that courts in one state will honor the judgments of courts of another state without having to retry the case. This helps form a true union among the states into one nation.
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 be general Laws prescribe the Manner in which such Acts, Records an Proceedings shall be proved, and the Effect thereof." (Article IV, Section 1)
This clause has three major effects. First, it requires recognizing and enforcing judgments in other states. Second, it limits the application of local state law when another state's law might apply to a multistate dispute. Third, this clause requires a state to open its courts to claims that arise in other states, if the state allows similar local lawsuits. This clause also prohibits a state from monopolizing litigation at the expense of other state courts.
The clause is commonly used to require a state to recognize marriages and divorces obtained in other states, but Congress has authorized a new state to modify another state's orders concerning child support in divorces. The Defense of Marriage Act (DOMA), 28 U.S.C. 1738c, enables each state to refuse to recognize another state's grant of same-sex marriages.