Law is a system of rules imposed by a place or authority to govern the behavior of its people. It has four main purposes: establishing standards, maintaining order, resolving disputes and protecting liberties and rights. The specific laws that exist depend on the type of society, its history and its relationship to other societies and to international norms. A legal system may be based on a constitution or on the decisions of a court or an elected legislature.
In modern legal systems a constitution establishes the basic structure of laws and rights. It may include such things as the separation of powers between different branches of government, the right to a trial by jury, and the freedom of the press. Individual states, regions or countries may have their own local laws to regulate the activities of its citizens and to keep them safe from internal and external threats.
Most modern law is written and voted on by representatives of the governed, who are called legislators or parliamentarians. A few countries, such as Burma and Zimbabwe, have authoritarian governments that impose their own laws on their subjects without being accountable to any other group or power. The laws made by these types of nations may be draconian, oppressing minorities or allowing them little opportunity for change.
The field of law has many subfields and specialties. Tort law deals with compensation for harm done to persons or their property, such as in automobile accidents or defamation. Employment law involves the tripartite industrial relationship between worker, employer and trade union; it includes things like labor contracts, wage and hour regulations and the right to strike. Criminal law is the set of rules enforced by a government to prevent or punish offenses against the state or its members, such as theft or murder.
In common law jurisdictions, judges or other adjudicators must decide what the law is in a particular case. This process begins with ascertaining the facts and locating any relevant statutes and cases. Then, a judge or other adjudicator must use principles, analogies and statements by previous judges in similar situations to determine what the law is in this case. This is known as the doctrine of stare decisis, and it assures that future courts will reach similar decisions. The decisions are then published in legal reports, which were first published as a public service by Massachusetts after the American Revolution and later became a function of the federal courts. Private publishers, such as West Publishing in Minnesota, supplement the government reports with indexing and editorial analysis to make them more useful to researchers.