Law is a system of rules created and enforced by social or governmental institutions to regulate behavior. Its precise definition is a subject of long-standing debate. Laws may be passed by a legislative process that results in statutes, decreed by the executive branch through regulations, or established by judges through case law, which is binding on lower courts under the “doctrine of stare decisis” (Latin for to stand by decisions). Laws may also be private, including contracts that are legally binding. Laws can be influenced by a constitution, written or tacit, or by the ideas encoded in a belief system such as principles of natural justice or the will of a deity.

The field of law has broadened from the core subjects of criminal and civil law, which deal with the resolution of lawsuits between individuals or organizations, to virtually all areas of human activity. For example, labor law involves the tripartite relationship between worker, employer and trade union and includes collective bargaining and the right to strike, while environmental law concerns the preservation of the environment and laws that govern governmental and private property. Tax law encompasses the laws governing how people pay taxes, while bankruptcy law deals with the procedures that may be used to wind up the debts of bankrupt companies.

The study of law has provided a source for scholarly inquiry into such areas as legal history, philosophy, economic analysis and sociology. It has also raised controversial issues of equity and fairness.

Legal scholars have developed a number of ways to organize the study of law. The most traditional approach divides it into three core subjects, each encompassing many related subfields:

Civil and criminal procedure – The rules that courts must follow as they decide cases in the trial and appeals processes. These include rules for choosing a jury, presenting evidence and determining whether a judge should rule in a particular way. This is called the “law of the case.”

Administrative law – The law that governs how governments operate and the agencies they create to carry out their functions, such as public utilities, police departments and prisons. This area of law is influenced by the principles of constitutional law, the doctrine of separation of powers and the concept that all government agencies must be accountable to citizens.

Family law – The laws that govern marriage and divorce proceedings, the rights of children and alimony payments. This area of law is influenced by concepts of equality, fairness and privacy. Criminal law – The laws that define the kinds of conduct that are considered harmful to society and that can be punished by criminal sanctions, such as imprisonment or fines. This area of law is influenced in turn by the social and moral theories of Max Weber, who reshaped thinking on the extension of state power over ordinary citizens.