Until the feds got involved, states could not enforce out of state orders. A state court has no jurisdiction over anyone living outside of their state borders. Someone can win a judgement over you from a state you don't live in, but your state is not only not obligated to collect it, their hands are tied & they can't collect from you, except if your case is covered under universal code.
See URESA, UIFSA & RURESA
http://www.baucomlaw.com/uresa.htm
An example would be when a parent with obligations has gone missing...
http://www.policyalmanac.org/social_welfare/archive/child_support_02.shtml
Cross state border custodial interference (it's not kidnapping when a parent does it) are another time that the federal courts will get involved. You send your child to their parent living in another state, required of you with a lawful court order & the other parent refuses to return the child, what do you do? Your local police will tell you that your child has not been kidnapped. It's between private parties. Unless you can prove cause for your children being in danger, you get your tush to a federal district court & file for an emergency ex parte hearing, so you can get a federal ruling to get the other state to send your child back.
Then we get into situations where one of the parents is another nationality, a citizen of another country. Some countries have treaties with the US to recognize each other's custodial orders, some do not. I believe it's covered under some kind of Hague treaty & never assume that all western democracies are parties to it, some aren't.
Members of our armed services are subject to a whole nother set of laws. Though, I can't remember the alphabet soup that covers them off the top of my head.
Thanks for posting, I didn't know any of that.