Private International Law is the body of law that governs private relationships that cross national borders. In the United States, we often refer to it as "Conflict of Laws" or "Choice of Law," because the central concern is the determination of which nation's laws will govern a transnational matter. But the substantive rules that will apply are also a part of private international law. The American Society of International Law defines it as "the body of conventions, model laws, national laws, legal guides, and other documents and instruments that regulate private relationships across national borders."
National laws are the primary sources of Private International Law, but is also embodied in treaties and conventions, model laws, legal guides, and other instruments that regulate transactions.
PIL deals with a variety of topics, such as international contracts, torts, family matters, recognition of judgments, child adoption and abduction, real property, and intellectual property.
1. Consult secondary sources to get a general overview of the topic and discussion of where to find applicable law, and to determine whether a treaty applies.
2. If no treaty or regional agreement applies, do the individual jurisdictions have any choice of law rules? In civil law countries, these rules are often set out as preliminary provisions to the basic codes. Again, secondary sources can be helpful in directing you to the governing rules. Start by consulting the Foreign Law Guide. Check references under the topic of "Conflicts of Law and Private International Law" for the country in question.
3. If national law applies, research the law of the foreign jurisdiction.