All states and the District of Columbia have enacted a statute called the Uniform Child Custody Jurisdiction Act, which sets standards for when a court may make a custody determination and when a court must defer to an existing determination from another state. In general, a state may make a custody decision about a child if (in order of preference):

• the state is the child's home state -- this means the child has resided in the state for the six previous months, or was residing in the state but is absent because a parent has removed the child from or retained the child outside of the state
• there are significant connections with people -- such as teachers, doctors and grandparents -- and substantial evidence in the state concerning the child's care, protection, training and personal relationships
• the child is in the state and has been either abandoned or is in danger of being abused or neglected if sent back to the other state, or
• no other state can meet one of the above three tests, or a state can meet at least one of the tests but has declined to make a custody decision.

If a state cannot meet one of these tests, even if the child is present in the state, the courts of that state cannot make a custody award. Also, a parent who has wrongfully removed or retained a child in order to create a home state or significant connections will be denied custody. In the event more than one state meets the above standards, the law requires that only one state award custody. This means that once the first state makes a custody award, another state can neither make another "initial" award nor modify the existing order.

Having the same law in all states helps achieve consistency in the treatment of custody decrees. It also helps solve many of the problems created by kidnapping or disagreements over custody between parents living in different states.