Almost every state has passed the Uniform Child Custody Jurisdiction and Enforcement Act (except Massachusetts and Vermont). Prior to the UCCJEA, state courts would often compete with one another for jurisdiction over a case. Essentially, if a parent did not like the result in one case, he or she would travel to a new state and file a competing lawsuit. The UCCJEA requires state courts to respect the initial court's decision and can only disturb the ruling in rare circumstances.
The UCCJEA imposes a three-part test. If a state can meet one of the tests, then it can assert jurisdiction over a child custody matter. The effect of the tests prevents people from "shopping" around for a favorable jurisdiction. This post will discuss the first part of the test and a follow-up will address the remaining two parts.
Under the first test, a state may assert jurisdiction if it resides in the child's home state. A child's home state is any state in which the child has resided for at least six months prior to legal action being brought. Or, a child would have been a resident in the state but for the fact that a parent removed the child from the state (i.e. "familial kidnapping").
If you are involved in a child custody dispute that crosses state lines, you probably will want the assistance of a family law attorney. These cases address complex issues regarding the jurisdiction of competing courts and how to square, often, competing laws. You don't need to figure these complex legal questions out on your own, a lawyer can help.