conflict of laws, that part of the law in each state, country, or other jurisdiction that determines whether, in dealing with a particular legal situation, its law or the law of some other jurisdiction will be applied. An alternative term, widely used in Europe, is "private international law." An example of a situation that might involve the different laws of two places is that of a contract signed in one state and mailed to another. Complications may arise if one of the states provides that a contract so delivered is effective once mailed, while the other state provides that it is not effective until received. The conflict of laws rules that a court applies in these disputed situations are commonly designed to decide the case by the law of the territory having the closest connection with the transaction. An often expressed ideal is that of making the decision the same regardless of where the case is decided.
In the United States the existence of many states with legal rules often at variance makes the subject of conflict of laws especially urgent. The Supreme Court ruled in 1938 that each federal court must apply the conflict of laws rules of the state in which it sits. Certain provisions of the U.S. Constitution deprive the states of complete freedom to determine how they will decide cases in this field. Most important is Article 4, Section 1, which provides, in part, "Full Faith and Credit shall be given in each State to the Public Acts, Records, and judicial Proceedings of every other State." The U.S. Supreme Court has interpreted this provision as requiring each state to treat as valid any judgment rendered by another state that had jurisdiction over the matter and to lend its powers of enforcement to the judgment; the sole exception is that the courts of one state do not enforce claims arising under the penal law of another (see extradition). Jurisdiction in this context is defined as the capacity of the state to impose its authority on a transaction because of its intimate connection with the litigants and/or the subject of litigation.
There are especially difficult jurisdictional problems in the field of divorce. The chief problem occurs when only one of the parties appears and the other is merely notified of the action. In such cases the Supreme Court has ruled that the state had jurisdiction to divorce if the party appearing was domiciled there. The court has defined domicile as the place where a person is living with the ultimate intention of making it his or her home. A person who obtains a divorce under these circumstances may seek alimony, or payment thereof, in any state and is immune from the charge of bigamy if he or she remarries.
The most important attempt in antiquity to deal with the problem of conflict of laws was the jus gentium [law of nations] of the Romans: a system of laws applied to all free foreigners. The founder of the modern study of conflict of laws was the medieval jurist, Bartolus of Sassoferrato (1314–57).
See W. W. Cook, The Logical and Legal Basis of the Conflict of Laws (1942); P. C. Jessup, Transnational Law (1956); S. A. Bayitch, Conflict of Laws (1968); J. G. Collier, Conflict of Laws (1988).