Law is a set of rules established in a society that regulates conduct and confers rights. A system of laws may consist of legislation, case law or custom. It may also include administrative law (rules created by governmental agencies) or constitutional law (a country’s supreme law).

Law covers a broad range of subjects, and the following list is not exhaustive. The core subjects are criminal law, property law, and civil law. Other areas of law include labour law, family law, immigration law, and copyright law.

There are many theories of what constitutes law, and there are debates about how the laws should be written and enforced. Some theories of law focus on the nature of humans and what is morally right and wrong. Others are based on empirical observations of the human world and its limitations.

The purpose of a legal system is to serve several goals: to keep the peace, maintain social order, protect individuals and groups from oppression, preserve the environment, promote social justice, and provide for orderly and controlled social change. Some systems serve these purposes more effectively than others. For example, an authoritarian government may keep the peace and maintain social stability but it may also stifle freedom of expression and oppress minorities.

A key issue in any legal system is how to define what is legally actionable and what constitutes a crime. These definitions are important because they form the basis of a country’s legal culture.

In a law-based society, laws are enacted by legislatures or created through judicial decisions. In a common law legal system, the decisions of higher courts are binding on lower court judges through the doctrine of stare decisis. This is different from a civil law system, where legal principles are codified in statutes or regulations and judge decisions are typically less detailed.

A court’s decision on a legal matter is usually published in a case judgment, which is often referred to simply as a case law. A case law is a legal opinion that provides a basis for future judicial decisions. Case law explains what a court will likely do in a similar situation, but it is not always completely predictable.

The governing principle of the rule of law is that all citizens and institutions are accountable to laws that are publicly promulgated, equally enforced, and independently adjudicated. It is a principle that requires measures to ensure supremacy of the law, equality before the law, accountability to the law, legal certainty, separation of powers, participation in decision-making, and avoidance of arbitrariness.

The law is also the source of social norms, standards and values, as well as ethical principles and the legal profession. Law reflects and reinforces a society’s beliefs about the correct and acceptable behaviour of its members, and it serves as an important channel for social change. For more, see jurisprudence; legal ethics; legal education; and constitutional law.