Law is a set of rules created and enforced through social or governmental institutions to regulate behavior. Its precise definition is a matter of longstanding debate and has been described as both a science and an art. Law aims to create an ordered society where conflicts between individuals and between groups are settled peacefully. It also protects the rights of individual citizens. It is a powerful tool in the hands of governments and it can have an enormous impact on the lives of individuals.

Whether it is property law governing ownership of land or civil rights laws protecting the freedom of speech, law influences our daily lives in many ways. It shapes politics, economics and history and governs the relationships between nations. It is a complex subject with countless areas of specialization. For convenience, we can divide it into three broad categories:

The first is the law as a political institution, the second law as a set of social principles and the third law as a set of rules governing legal procedures. In the first category are subjects such as constitutional law, public policy, political economy and international relations. These subjects are fundamental to our understanding of the law.

Governments can make laws to regulate the behavior of their citizens or a community and they may enforce these laws through judicial action, decrees or statutes. These laws can be influenced by a constitution, written or tacit, and the rights encoded within. They can be made by a collective legislature, resulting in statutes, by the executive, through decrees and regulations or by judges through precedent. Private individuals can also create legally binding contracts or arbitration agreements.

In addition to the laws that are publicly promulgated and enforced by a nation-state, there is a body of law that applies throughout the world. This global body of law, often called international law, contains more than 500 multilateral treaties deposited with the United Nations and a growing body of national legislation and case law.

This international law provides an additional layer of protection for individuals and their rights. For example, an international convention can provide a remedy for violations of human rights that are not covered by domestic law. The international law that is made by and for nations is constantly changing and developing, as the needs of modern societies change.

The rule of law is a principle of good governance that states must be accountable to laws that are publicly promulgated and equally enforced, independently adjudicated and fair to all. It also includes adherence to internationally recognized human rights standards.

Despite their differences, legal systems around the world do fall into some groups with similarities based on historically accepted justice ideals. Most countries employ multiple systems of law at the same time to create a hybrid system. The law that is used in most of the world is a civil law system, derived from codifications in constitutions and statutes passed by the government or by custom and tradition.