Law is the system of rules that a country or community recognises as regulating its members’ actions. Its purposes include establishing standards, maintaining order, resolving disputes and protecting liberties and rights. For an analysis of its role in the administration of government, see administrative law. For an exposition of social restrictions and their enforcement, see censorship; crime and punishment; and police. The study of law also involves an exploration of legal philosophy.

A ‘pure theory of law’ proposed by Hans Kelsen suggests that the existence of laws does not imply that everyone will abide by them or that all will do so in the same way, and that they are therefore no more than guidelines which people may choose to follow or ignore. This theory contrasts with Max Weber’s more sociological view, which holds that the function of law is to control society and to satisfy a range of social wants, such as the need for security, property and freedom.

Legal systems vary widely around the world, influenced by both constitutional and judicial structures, and historical and cultural influences. The broad areas of the law are contract, property, family and international. Contract law covers agreements to exchange goods or services, from the purchase of a bus ticket to trading options on a stock market. Property law defines people’s rights and duties toward tangible personal possessions, including land and movable things such as cars and jewellery. It distinguishes between a right in rem and a right in personam, which are the two types of ownership that may exist for real estate.

Family law covers marriage and divorce proceedings and the rights of children. In some jurisdictions, the law is defined by religious tradition. In others, it is governed by the jurisprudence of a particular court or judge. International law outlines the relations between nation-states and their citizens, and is influenced by the principles of human rights and the rule of law, which define healthy societies.

The practice of law involves a range of careers, from advising clients about their legal options and representing them in court to ensuring that the justice system operates fairly. A variety of ethical debates occur around this subject, such as the extent to which judges should be independent from political interests and whether they should be allowed to express their own moral views on a case. See the articles on legal profession; legal education and training; and legal ethics for more information.