Law is the set of rules a community establishes and enforces to govern behavior and protect the interests of its members. It serves four primary purposes: setting standards, maintaining order, resolving disputes, and protecting liberties and rights. Law is often based on a written code, but it can also be inferred from an authoritative body of precedents, or created by private individuals through legal contracts. It can be enacted by legislatures through statutes, decrees, or regulations; enforced by executive authorities through orders and penalties; or established by judges through case law. The precise definition of law varies from jurisdiction to jurisdiction.
In a broad sense, any rule imposed by an authority that must be followed can be considered a law. Most commonly, however, law refers to a system of enforceable, publicly disclosed rules created and enforced by a government that regulates social activity and imposes consequences for breaking them. Typically, laws are interpreted and applied in a fair and impartial manner, regardless of one’s wealth or status.
Legal systems exist in many forms worldwide, and they differ from country to country in the nature of the rules they impose and the penalties they levy for breaking them. Generally, they fall into one of three categories: statutory law, common law, and civil law. Statutory laws are enacted by legislatures and typically contain clear and detailed definitions, requirements, and procedures for a particular situation. Common law systems rely on a judicial tradition that builds upon a detailed record of past decisions to evaluate legal matters and establish precedents. Civil law uses a standardized system of legal statutes that are enforceable by courts, and it is often used to resolve business or commercial disputes.
Federal law is typically based on the express grants of power outlined in the United States Constitution, which include powers related to the military, money (including taxation), foreign relations, transportation, patents and copyrights, and mail. It interacts with state and local law in areas like family, criminal, and immigration law. Increasingly, the scope of federal law has been expanded by interpretations of the Commerce and Spending Clauses of the Constitution in areas like air and railway transportation, pharmaceuticals, antitrust, and trademarks. This expansion of federal law is referred to as federalism.