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 Massachusetts, as in other states, the issue of which jurisdiction's laws apply to a lawsuit or dispute is governed by the principles of conflict of laws, also known as choice of law rules. These rules are designed to resolve questions of which state or jurisdiction's substantive law should be applied when there are competing jurisdictions connected to the parties or the circumstances of the case. Massachusetts courts will consider various factors, such as the place where the injury occurred, the place where the conduct causing the injury occurred, the domicile, residence, nationality, place of incorporation, and place of business of the parties, and the location where the relationship between the parties is centered. When a contract is involved, Massachusetts courts will typically honor a choice of law provision within the contract, as long as the chosen law bears a reasonable relation to the parties or the transaction and is not contrary to a fundamental policy of a state with a materially greater interest. In cases without a contractual choice of law clause, Massachusetts courts will apply the most significant relationship test to determine which state's laws should govern the dispute. This approach is consistent with the Restatement (Second) of Conflict of Laws, which is a legal treatise widely recognized by courts to provide guidance on conflict of law issues.