Law is a system of rules created and enforced through social or governmental institutions to regulate behavior. Its precise definition is a matter of longstanding debate. Unlike some of the other subjects studied in this encyclopedia, law cannot be empirically verified; it is a system of normative principles.
Law shapes politics, economics, history and society in many ways, and serves as a mediator between relationships among people. Its form can be state-enforced, as in civil law jurisdictions, where statutes and regulations are the main sources of law; or privately established through contract law, as in common law systems.
Regardless of its form, any legal system must adhere to the principle of supremacy of law, equality before the law and accountability under the law. It must also ensure that its laws are publicly promulgated, equally enforced and independently adjudicated and must avoid arbitrariness.
A fundamental aspect of law is the idea of right, a concept that is central to the development of jurisprudence and the philosophy of law. According to Hohfeld, rights may be grouped into four categories: claim-rights, power-rights, value-rights and instrumental-rights. Each of these is associated with a duty, which may be owed or required by a person to another.
In order to be a law, a rule must be permanent as to time; it must be uniform as to all persons, meaning that the same standard is applied to everyone. It must also be universal as to place, meaning that the same standard applies everywhere in a given jurisdiction. A legal system must therefore be based on rules that are easy to learn and apply. It should not be so complex that it is only available to the elite.
The study of law has numerous subfields, including constitutional law; commercial law; criminal law; employment law; family law; inheritance law; international law; property law; and tort law. It is also possible to specialize in the practice of law, which involves the preparation and defense of cases before a judge or jury. It is a profession in which the title Esquire, or Doctor of Law, is used to indicate that one has completed a degree program in law and is qualified to represent parties before the courts.
A large number of nations, ranging from ancient civilizations to the most modern of democracies, have some form of legal system. Most of the world’s nations use a combination of civil and common law, with the law of a particular nation typically being influenced by its cultural traditions. In some nations, such as Egypt, Africa and South Pacific islands that once were colonized by continental European countries, the civil law tradition is still in force today. The Napoleonic and German codes are among the most influential codifications of civil law. In mixed jurisdictions, the civil code is combined with other traditions such as Islamic Sharia law.