Law is a body of rules established and enforced by social or governmental institutions to regulate behaviour and protect private and public rights. It has been variously described as an art, a science and an instrument of justice. The precise nature of the law is a matter of debate and varies from society to society. A law can be created by a group legislature, resulting in statutes; by the executive, through decrees and regulations; or by judges, through precedent (usually in common law jurisdictions). Individuals may also create legally binding contracts and arbitration agreements that adopt alternative ways of resolving disputes to standard court litigation.
A legal rule is a statement of an invariant relationship between phenomena under specified conditions. For example, Boyle’s law states that the volume of a gas is proportional to its temperature and pressure. Laws are based on facts, principles and judgments, but may also be influenced by values and preferences. The word law is derived from the Latin word lex, meaning a custom or rule. Some laws are based on the natural sciences, such as Newton’s law of universal gravitation: Fg = G(m1+m2)2/d where m1 and m2 are the masses of the objects and d is the distance between them. Other laws are based on human experience and understanding, such as the law of cause and effect.
Most legal systems are based on either civil law or common law. The distinction between the two is somewhat artificial, as modern law often combines elements of both. Historically, the main functions of law have been to keep the peace and maintain the status quo, preserve individual rights and freedoms, ensure that the needs of minorities are met and provide for orderly social change. Some legal systems do these things better than others.
The principal function of a nation’s government is to make and enforce the law. The political landscape varies from country to country and some governments are less capable of performing this function than others. Authoritarian regimes, for example, are often incapable of maintaining the peace or preserving individual rights and freedoms. In contrast, democracies can be unstable and fail to meet the needs of minorities.
In the United States, laws are made by Congress and signed into effect by the President. If the President vetoes a bill it is returned to Congress with a note explaining his/her reasons. If the veto is overridden in both chambers, the bill becomes a law. After each session of Congress, slip laws are compiled into a book called the U.S. Statutes at Large. Laws can also be incorporated by reference to other sources, such as the constitution, treaties or decisions of international tribunals.