Law is the system of rules a community recognizes as regulating the actions of its members. It can be the basis of a constitution, a political party, or an ideology. It may govern economic activity, property rights, or even criminal activities. Its study is called legal science.
In the modern West, law is mainly a product of human elaboration and evolution. Philosophers debate the extent to which it incorporates morality. Utilitarians like John Austin believe that the primary function of law is to achieve social justice, but other theories, including those of Jean-Jacques Rousseau and Thomas Aquinas, posit that law is based on natural and unchanging laws of nature.
Legal systems vary widely among nations and regions of the world, but all share certain elements. Some include legislative statutes and executive regulations; courts of law that enact or enforce laws; judicial decisions (called “case law”); and the system of precedent that allows decisions in similar cases to influence future ones.
Most laws are created and enforced by the state, but some are a product of religion or culture. For example, Islamic law is based on the Quran and further elaborated through the principles of interpretation (Qiyas), consensus (Ijma), and jurisprudence (Halakha). Jewish and Christian canon law are also derived from religious precepts and are the source of law in their respective communities. These laws, however, are not necessarily universally binding. Other laws are based on military action and foreign policy (international law) and the rules of international treaties, tariffs, and intellectual property rights (trademarks and copyrights). These are called public law.