Law is a system of rules established and enforced by social or governmental institutions to regulate behavior and establish rights and responsibilities. It may be created by a legislature, resulting in statutes; issued by the executive through decrees and regulations; or established by judges through precedent, notably in common law jurisdictions. Private individuals may also create legally binding contracts, including arbitration agreements that adopt alternative ways of resolving disputes to standard court litigation.

The precise definition of law is a matter of longstanding debate, but generally speaking it refers to the aggregate set of rules that a sovereign sets over its subjects, and which are enforced through a variety of mechanisms, including sanctions. Some argue that the law is simply power—that, regardless of the quality or justness of the laws, they are obeyed because of the threat of coercion that accompanies their enforcement. This argument is most frequently advanced by those who believe that tyrannical rulers such as the Nazis and Saddam Hussein exercised their power in accordance with law.

Other theories of the law emphasize its role in the protection of human rights and freedoms, or as a tool for economic development and social stability. The study of law involves a wide range of fields, from labor law to the regulation of competition, from criminology to international law. Often the subject is divided into broad categories or ‘titles’, such as criminal law, family law, corporate law, and civil law.