When there is more than one state, or more than one jurisdiction (state court, federal court) with a significant relationship to the parties and circumstances involved in a lawsuit or dispute, the question may arise as to which state or jurisdiction’s laws will govern the lawsuit or dispute. The body of law that determines what law governs a dispute is called conflict of laws and consists of legal principles courts use to determine which state or jurisdiction’s law applies—unless the parties to a dispute have agreed (usually in a contract) on what law will apply.

In New Hampshire, as in other states, the issue of which jurisdiction's laws apply to a legal dispute is governed by the principles of 'conflict of laws' or 'choice of law.' These principles are designed to resolve questions of which state or jurisdiction's substantive law should be applied when a case has connections to more than one jurisdiction. New Hampshire courts will typically use a 'most significant relationship' test to determine which state's laws are most appropriate to apply to the issues in a case. This involves examining factors such as where the parties are located, where a contract was entered into or where a tort occurred, among others. However, if the parties have entered into a contract that includes a choice of law provision, the courts will generally honor that agreement, provided it was made in good faith and does not contravene public policy. In cases involving federal law or where jurisdiction is based on federal question jurisdiction, federal law may apply regardless of the state law. It's important to note that choice of law issues can be complex and may require the assistance of an attorney to navigate.