Law is the set of rules created and enforced by social or governmental institutions to regulate behavior. The precise definition of law is a matter of debate. The American Heritage Dictionary of the English Language defines it as “a body of principles or rules regulating some aspect of human activity and enforceable by a governing authority.” The term law is also used to refer to a particular system of laws in a country or region. In the United States, federal law encompasses both state and federal statutes and regulations and covers areas such as criminal, bankruptcy, family, civil rights, copyright, evidence, property, tax, and administrative law. A state’s constitution, statutes, and court decisions also constitute its law.

Several philosophical schools of thought have addressed the question of what is law. One school views law as a set of rules that are binding and enforceable. This view is generally called natural law. Another philosophy views law as a moral code that is derived from reason and divine revelation. A third philosophy sees law as a system of rules and regulations based on the needs of society and individuals.

A legal scholar, Michael Hohfeldian, describes the law as a set of rules that determines what right-holders may or cannot do. These rules, he says, are not objective but rather subjective and largely dependent upon the values of the society in which the law is produced. Hohfeldian also distinguishes between active and passive law. Active law determines what right-holders ought to do, while passive laws decide what they can or cannot do (Loon 1970; Sumner 1987: 275).

The purposes of law are generally seen as being to keep the peace, maintain the status quo, preserve individual rights and liberties, promote social change, protect minorities against majorities, and provide for orderly and efficient government. Some legal systems are more effective at fulfilling these purposes than others. For example, an authoritarian regime can keep the peace and maintain the status quo but may oppress minorities or suppress political opponents. A democratic government, on the other hand, is more likely to promote social change and protect minorities.

Other aspects of law include case law, precedent — the decision of an earlier court that has facts and issues similar to those in a current dispute — and the Rules of Procedure. Case law consists of past court decisions that are binding upon the courts, although they can be overturned. A judge may use case law to interpret and apply other laws such as statutes. The Rules of Procedure outline the process of conducting a trial and include rules of civil, criminal, bankruptcy, and appellate procedure.

In a trial, the judge will give instructions to the jury regarding what law applies to the facts of the case. These instructions are known as the charge to the jury. The trial will usually involve testimony from witnesses who will describe what happened. The judge will then ask the jury to determine whether the defendant is guilty of a crime. In some trials, the jury will be sequestered and shielded from spectators to ensure that they can reach a unanimous verdict.