Civil law is a major "branch of the law", in common law legal systems including those in England and Wales and in the United States, where it stands in contrast to criminal law. Private law, which relates to civil wrongs and quasi-contracts, is part of civil law, as is contract law and law of property. Civil law may, like criminal law, be divided into substantive law and procedural law. Substantive law refers to the determination of how the law applies to facts, and procedural law refers to regulations on how the substantive law is administered. The rights and duties of persons amongst themselves are the primary concern of civil law. The common law is today as fertile a source for theoretical inquiry as it has ever been.