Law is a system of rules created and enforced by social or governmental institutions to regulate behaviour and to ensure the security and rights of individuals and communities. It can be state-enforced (through legislation, either collectively or by a single legislator, resulting in statutes), executive decree or regulation, or judge-made by case law in common law jurisdictions. It can also be private or community-enforced through agreements enforceable by courts, such as contracts and arbitration agreements. Law shapes politics, economics, history and society in many ways. It is a major subject of scholarly inquiry in philosophy, sociology and political science.

Criminal law deals with conduct considered harmful to society and which is punishable by imprisonment or fines. Civil law deals with the resolution of lawsuits (disputes) between individuals or organisations. Laws that govern international affairs, such as those governing space, are known as international law. Laws governing the transport of goods, such as maritime law or air law, are known as commercial law. Laws governing banking and finance are known as financial law.

In some societies, laws are codified in a constitution or other written document. In others, they are based on custom and tradition. For example, Sharia law is a religiously influenced legal system that governs some parts of the world. Modern philosophies of law have been reshaped by the likes of Max Weber and others, reflecting concerns about the extension of the state into areas that were previously left to community management or privately owned activities.