Customary law or jurisprudence is the law declared by judges. The laws that govern a country are a fundamental element of its existence and provide the framework within which a society operates. In addition to common law and statutory law, there are also regulatory laws drafted by various government agencies that are authorized to do so once the legislature has created the laws. A basic rule of legal interpretation is the presumption that the legislature does not intend to change common law unless expressly stated in the legislation.
Common law is binding on all courts in the jurisdiction, while law is only binding on the court in which it was enacted. The determination of statutory law generally begins with the same research process as common law, but it can also include an analysis of the legislative history of the law. Statutes are approved by Congress or state legislatures and enacted into law by the president or governor. An example is the Occupant Liability Act, discussed in my previous legal column, which replaced the duty of care required by common law for occupants of facilities.
Customary law is also known as jurisprudence and is of two types: one in which sentences handed down become new laws where there are no statutes and another in which judges interpret existing law and determine new limits and distinctions. In a civil law system, statutory law is the primary source of law, and common law plays a relatively minor role. For more than a century, criminal law has been codified in the Criminal Code, but the concepts of mens rea (intention) and natural justice in common law continue to influence jurisprudence. Legislation can codify common law by giving legal force to the principles of common law without completely displacing common law.
For example, if a law is found to be unconstitutional, the courts will overturn it and common law will take its place. However, a court judgment based on common law principles would be binding on both state and federal courts. Common law is derived from judicial precedent, while statutory law is derived from legislative action.