List of national legal systems
Common law is currently in practice in Ireland, most of the United Kingdom (England and Wales and Northern Ireland), Australia, New Zealand, Bangladesh, India (excluding Goa), Pakistan, South Africa, Canada (excluding Quebec), Hong Kong, the United States (on a state level excluding Louisiana), and many other places. In addition to these countries, several others have adapted the common law system into a mixed system. For example, Nigeria operates largely on a common law system, but incorporates religious law.
International law
The modern study of international law starts in the early 19th century, but its origins go back at least to the 16th century, and Alberico Gentili, Francisco de Vitoria and Hugo Grotius, the "fathers of international law." Several legal systems developed in Europe, including the codified systems of continental European states and English common law, based on decisions by judges and not by written codes. Other areas developed differing legal systems, with the Chinese legal tradition dating back more than four thousand years, although at the end of the 19th century, there was still no written code for civil proceedings.