People often relocate after they are divorced or if not married after they resolved their issues of child support or child custody. A common question comes up when one person remains in New York and the other person has moved to another state as to whether any new litigation about child support or custody/visitation should be decided in New York or the other state.
The basic rule is that if either person is still a New York resident and there is a New York Order in effect then New York keeps the case under the doctrine of "continuing exclusive jurisdiction". The concept simplified is that a person who remains in New York with a New York Order in place will continue to receive the benefits (if you want to call it that) of New York laws and not be forced to have a new state's laws applied when the New York resident has no connection with the other state.
So for example a New York child support order that runs to age 21 will not be reduced because a parent has moved to a state where child support ends at 19. Likewise, a parent who remains in a state where child support ends at 19 and that state issued the original order then the parent who remained will not have to pay after age 19 because New York will not make the parent pay to age 21 because the first state emancipated the child at an earlier age. Further modifications have to be sought in the original state if a parent continues to reside there. Where neither parent lives in New York, then the case will usually be handled in the state where the parent and child reside. However, the Court might still apply New York law to the case.
Custody cases generally follow the same rule that the original state if a parent still resides there has "continuing exclusive jurisdiction", but there is a big exception. The original state can "decline" to keep the case if in keeping the case it would be inconvenient or difficult to properly handle the case. An example is that the residential custodial parent and child live out of state and New York realizes that it will be difficult to try the case because the necessary witnesses and the child live in a different state. It would be hard or perhaps impossible to obtain the testimony of neighbors, coaches, teachers and doctors from the new state where the parent and child reside as those witnesses will be unavailable in New York and may have important personal knowledge that the Court would need to decide the case.
This area of the law is complicated and at best the above is a brief simplified summary of the major concerns. If these issues arise it is important to have an experienced matrimonial/family law attorney to provide proper advice.