What type of jurisdiction does a court have if no state has home-state or significant-connection jurisdiction?

When no state has home-state jurisdiction or significant-connection jurisdiction, a court can exercise what is referred to as default jurisdiction. Default jurisdiction allows a court to take jurisdiction when there are no other states that have a legitimate claim to the jurisdiction based on the child's residence or the connections of the parties involved. This often comes into play in custody disputes where the applicable statutes do not confer jurisdiction on any particular state under the Uniform Child Custody Jurisdiction and Enforcement Act (UCCJEA).

This type of jurisdiction is essential in ensuring that there's some avenue for the resolution of custody matters, even when typical jurisdictional criteria are not met. Without default jurisdiction, a child's custody case could potentially remain unresolved due to jurisdictional conflicts or issues.

In contrast, other types of jurisdiction mentioned have distinct purposes and requirements. For example, exclusive continuing jurisdiction would apply if a court previously made a custody determination and one of the parties still resides in that state. Shared custody jurisdiction refers to situations where multiple states have claims to jurisdiction, while best interest jurisdiction is not formally recognized as a standalone concept in Family Law; rather, it is an overarching principle applied once jurisdiction is established.