Private international law(a.k.a., conflict of laws) is the body of conventions and model laws that regulate private relationships across national borders; e.g., divorce law or the law relating to the sale and transport of goods. Private international law is that branch of international law and interstate law that regulates all lawsuits involving a “foreign” law element, where different judgments will result depending on which jurisdiction’s laws are applied. Private international law addresses the questions of (1) in which legal jurisdiction (i.e., which legal bodies entitled to act) may a case be heard; and (2) the law concerning which jurisdiction(s) apply to the issues in the case law of supranational organizations.
Multilateral private international law treaties cover such areas as trade and commerce, finance and banking, trusts and estates, family and children (e.g., custody, adoption, etc.) matters, international judicial assistance, and regulations on real property, consumer law, currency control, insurance and banking. For ETO Consortium purposes, private international law matters concern those cases where regional or international agreements render the domestic laws of nation states inapplicable when conflicting with a supranational legal system.
In civil law systems, private international law is a branch of the internal legal system dealing with the determination of which state law is applicable to situations crossing over the borders of one particular state and involving a “foreign element” (élément d’extranéité), (collisions of law, conflict of laws, clash of regimes). Lato sensu (at large) it also includes international civil procedure and international commercial arbitration (collisions of jurisdiction, conflict of jurisdictions.
In common law systems, private law/conflict of laws is principally concerned with determining whether the proposed forum has jurisdiction to adjudicate and is the appropriate venue for dealing with the dispute. Secondly, it is concerned with determining which of the competing state’s laws are to be applied to resolve the dispute. It also deals with the enforcement of foreign judgments.
There are two major streams of legal thought on the nature of conflict of laws. One group of researchers regard Conflict of Laws as a part of international law, claiming that its norms are uniform, universal and obligatory for all states. This stream of legal thought in Conflict of Laws is called “universalism.” Other researchers maintain the view that each State creates its own unique norms of Conflict of Laws pursuing its own policy. This theory is called “particularism” in Conflict of Laws.
(See International law, public and private (compared))
 Rosslyn Higgins, Problems and Process: International Law and How We Use It (Oxford: Clarendon Press, 1994), p. 146.