Law is a set of rules created and enforced through social or governmental institutions to regulate behaviour. It is a source of scholarly inquiry into legal history, philosophy and economic analysis, as well as raising issues concerning equality, fairness and justice. The exact definition of law is a subject of dispute, and its precise nature has varied over time and place.
Law can be categorised broadly into three areas, though the subjects are often intertwined and overlap. Criminal law deals with the punishment of people who break public or private rules of morality or order. Civil law deals with disputes between individuals, and can be applied to matters such as contract law or tort law. The broader field of administrative law covers government regulation in areas such as air, tax or transport laws.
The common law tradition, found in countries such as England and the United States, places greater emphasis on precedent than on written constitutions or legislative statutes. It also emphasises the importance of justice and fairness, as opposed to merely being enforceable. Under this system, decisions of judges are considered to be “law” on equal footing with statutes and regulations issued by the executive branch. This is known as the doctrine of stare decisis, meaning that past decisions are to be followed in future cases.
In contrast, a civil law tradition, with its roots in Roman and canon law, is found on all continents. Its modern form is largely secularised and has a strong focus on individual freedom. In continental European nations, such as France or Italy, it coexists with a common law tradition.
Other forms of law may be explicitly based on religious precepts, such as Jewish Halakha or Islamic Sharia, and can also be influenced by these. Religiously based laws tend to be more complex and difficult to define, but can have a powerful impact on the culture of a country.
Other kinds of law can be derived from scientific theories or discoveries, such as the law of gravity or the law of supply and demand. These laws are normative and are meant to guide how people ought to act. Other laws, such as those governing medical practice or the use of weapons, are descriptive and reflect the experience and knowledge of expert groups in those fields. In the latter case, the experts are usually regulated by the relevant body of law. These bodies can be professional organisations, such as a medical board or a military court. They can also be constituted through treaties between states. These international agreements can govern areas such as space law or the carriage of goods by air, as well as banking and financial regulations. They can also encompass more general aspects of the law, such as tax law or evidence law. The rule of law, which is a key feature of the UN system, requires that all governments and private entities adhere to laws that are publicly promulgated, equally enforced and independently adjudicated.