The Full Faith and Credit Clause in Article IV of the United States Constitution is invoked primarily to enforce judgments. The clause states "Full Faith and Credit shall be given in each State to the public act, Record, and judicial Proceeding of every other State. And the Congress may by general Laws prescribe the Manner in which such Acts, records and Proceeding shall be proved and the Effect thereof". When a judgment is rendered by a court that has jurisdiction over the parties, the judgment must have the same legal effect in other states as well.
The Uniform Child Custody Jurisdiction Enforcement Act ("UCCJEA")
says that jurisdiction for child custody cases is determined by the child's
"home state" - the state where the child has lived for the past
six, consecutive months. Every state in the United States has adopted
the UCCJEA except for Massachusetts. The voluntary adoption of the UCCJEA
by 49 states recognized Article IV of the Constitution but set out the
procedures by which a state would make the Initial custody determination
for the child.
Prior to the UCCJEA and its predecessor "UCCJA", the first party to file a lawsuit would determine the state in which the case would proceed. One state had to recognize the judgment of another state under Article IV. This led to forum shopping and unfair resolutions of custody matters. Instead of Congress suspending Article IV of the constitution by allowing states to ignore unjust results in custody matters, they put forth a set of regulations which could be adopted by the states. The UCCJEA set forth the procedures each state has to follow in custody proceedings. It created subject- matter jurisdiction over the child, i.e. jurisdiction is based on the relationship between the child and the state, not the parent and the state.
After the court makes a child custody determination, it has continuing
jurisdiction over the case, with the exception of two circumstances. First,
the state will no longer have jurisdiction over the case if the child
or his parents is no longer connected with the state. Secondly, the state
will lose jurisdiction if another court determines that the child and
his/her parent does not live in the original state anymore.
Contrast the UCCJEA to "The Defense of Marriage Act (DOMA)" which created a full faith exemption for state recognition of same-sex marriage. The federal government suspended Article IV of the Constitution i.e. states which did not recognize same sex marriage did not have to give Full Faith & Credit to a state which did recognize same sex marriage. A reading of DOMA suggests that a sister state will enforce a valid custody or child support order even if that sister state does not recognize the legality of a civil union. But will that state accept jurisdiction on a petition to establish or challenge custody under the "UCCJEA ". Hopefully that issue will be rendered moot shortly by the U.S. Supreme Court.