Law is a set of rules established by social or governmental institutions to regulate human behavior. It is enforced by mechanisms such as police and courts, imposing sanctions for infractions or infringements. Law is a key element of any state, enabling it to function as a society that can ensure peace and protect the rights of its citizens.

The precise definition of law is a matter of ongoing debate. One of the earliest and most influential theories of law was Bentham’s utilitarian theory, which defined it as “commands, backed by the threat of sanction, from a sovereign to whom people have a habit of obedience.” Other legal philosophers, such as Jean-Jacques Rousseau, have argued that the nature of human beings is governed by unchanging moral laws.

In modern times, the concept of law has diversified to reflect the unique social, economic and historical conditions in different countries. Regardless of its specific form, the fundamental role of law is to establish and enforce order in a society, protecting individual rights and ensuring the peaceful transfer of power between individuals. Laws can be formulated by a legislature, resulting in statutes; by the executive, resulting in decrees and regulations; or by judges through precedent, known as common law. In addition, private individuals can create binding contracts and arbitration agreements, which are enforceable by the courts.

A law may be written or unwritten, explicit or implicit, secular or religious, domestic or international. In most modern nation-states, there are formal constitutional laws and judicial decisions that are recognized as law. These are often augmented by detailed legislative statutes and an official legal code. Laws can also be enacted through the practice of case law, in which judicial decisions are evaluated and used to determine future cases.

Some countries have unique legal traditions that blend secular and religious influences, such as Hindu or Islamic law. In such cases, the law is often based on a combination of scriptures, interpretation and jurisprudence, which is further elaborated through qiyas (reasoning by analogy), ijma (consensus) and precedent.

In the United States, for example, each state decides what conduct to punish, and each has its own criminal statutes. The federal government enacts some criminal laws, codified in Title 18 of the United States Code. In many countries, terrorism cases are heard in special courts designed to handle such crimes. Other countries have unified systems that include a common law criminal code and civil law. These include Japan, Malaysia and Brunei. These unified legal systems can be contrasted with other more diverse national legal traditions, such as those in India and Pakistan.