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 Washington State, as in other jurisdictions, the body of law known as 'conflict of laws' or 'choice of law' is used to determine which state or jurisdiction's laws should apply to a legal dispute when multiple jurisdictions are involved. This determination is crucial when the parties and the circumstances of a case have connections to more than one state or legal system. Washington courts will consider various factors, such as the location where a contract was signed or where an injury occurred, the residency of the parties involved, and the nature of the transaction or event that gave rise to the lawsuit. The courts aim to apply the law of the jurisdiction that has the most significant relationship to the issue at hand. However, if the parties have previously agreed on which jurisdiction's laws will govern their dispute, typically through a choice of law clause in a contract, Washington courts will generally honor that agreement, provided it is not contrary to a fundamental policy of the state and the chosen state has a substantial relationship to the parties or the transaction.