In child custody disputes in which the parents and children have significant contacts with more than one state—such as having homes in multiple states and spending significant amounts of time in multiple states—there may be a question of which state’s courts have jurisdiction over the child custody dispute (the authority to hear and decide the dispute). The Uniform Child Custody Jurisdiction Enforcement Act (UCCJEA) is a law adopted by most states (all but Massachusetts) that determines which state’s courts have jurisdiction to hear and decide a child custody dispute in such a situation.

In California, as in most other states, the Uniform Child Custody Jurisdiction Enforcement Act (UCCJEA) governs jurisdiction in child custody disputes involving multiple states. The UCCJEA aims to avoid conflicts between states in custody decisions, promote cooperation among states, and protect the best interests of the children involved. Under the UCCJEA, the child's 'home state'—defined as the state where the child has lived with a parent for at least six consecutive months prior to the commencement of the custody proceeding—generally has jurisdiction to make an initial custody determination. If the child has not lived in any state for six months, a state with significant connections to the child and at least one parent, and substantial evidence concerning the child's care, protection, training, and personal relationships, may assert jurisdiction. The UCCJEA also provides for enforcement of child custody orders across state lines and seeks to prevent re-litigation of custody decisions in other states, except under specific circumstances. California courts will apply the UCCJEA to determine whether they have jurisdiction to hear a child custody case when there are significant contacts with more than one state.