Conflict of laws (also called private international law) is the set of rules or laws a jurisdiction applies to a case, transaction, or other occurrence that has connections to more than one jurisdiction. This body of law deals with three broad topics: jurisdiction, rules regarding when it is appropriate for a court to hear such a case; foreign judgments, dealing with the rules by which a court in one jurisdiction mandates compliance with a ruling of a court in another jurisdiction; and choice of law, which addresses the question of which substantive laws will be applied in such a case. These issues can arise in any private-law context, but they are especially prevalent in contract law and tort law.

Scope and terminology.

The term conflict of laws is primarily used in the United States and Canada, though it has also come into use in the United Kingdom. Elsewhere, the term private international law is commonly used. Some scholars from countries that use conflict of laws consider the term private international law confusing because this body of law does not consist of laws that apply internationally, but rather is solely composed of domestic laws; the calculus only includes international law when the nation has treaty obligations (and even then, only to the extent that domestic law renders the treaty obligations enforceable). The term private international law comes from the private law/public law dichotomy in civil law systems. In this form of legal system, the term private international law does not imply an agreed upon international legal corpus, but rather refers to those portions of domestic private law that apply to international issues.

Importantly, while conflict of laws generally deals with disputes of an international nature, the applicable law itself is domestic law. This is because, unlike public international law (better known simply as international law), conflict of laws does not regulate the relation between countries but rather how individual countries regulate internally the affairs of individuals with connections to more than one jurisdiction. To be sure, as in other contexts, domestic law can be affected by international treaties to which a country is a party.

Moreover, in federal republics where substantial lawmaking occurs at the subnational level—notably in the United States—issues within conflict of laws often arise in wholly domestic contexts, relating to the laws of different states (or provinces, etcetera.) rather than of foreign countries.