Choice of law is usually thought of as a problem of law across geography, of how laws apply to persons and events not entirely within a state’s boundaries. But another dimension to the choice of law problem is that of time. In cases wholly domestic to a single state, this temporal issue appears when a court considers whether a change in law has retroactive application. But changes in law occur in interstate cases as well. Moreover, the facts relevant to a choice of law analysis may change between the time of the underlying events and the litigation. Does the court consider facts as they exist at the time of litigation or are the facts to be fixed as of the time of the underlying events? These questions appear in three contexts: First, the state whose law is to apply under a choice of law rule may undergo change, and the sovereign currently in force is not the same one that existed at the time of the events leading to the litigation. Second, the state remains the same but it has changed its law. Third, the facts relevant to choice of law may change over time. By drawing these three contexts together, one can get a sense of the larger problem of choice of law and time. In general, the question is whether rights and obligations of the parties should be fixed, anchored to a definite point in the past, or allowed to float and change over time. No single overarching solution is available, but the relevant factors are the nature of the underlying issue, the choice of law approach the court has taken, and the extent to which the policy demands of the present are impaired as compared to the impairment of the expectations and reliance interests of the parties who acted in the past.
Rensberger, Jeff, Choice of Law and Time (April 4, 2021).