Law is a system of rules and regulations enforced by a country or community. Oxford Reference provides more than 34,000 concise definitions and in-depth, specialist encyclopedic entries on all aspects of law—from criminal and civil rights to property and international treaties. Law is a complex topic with a long and varied history. Law is the basis of the Constitutions of all constitutional republics and sets up the structure of government; allocates power, authority, and responsibility; and protects liberties and rights. It serves many purposes, including establishing standards, maintaining order, and resolving disputes.
A legal system may be based on a constitutional republic, common law, religious or ethnic traditions, or any combination of these. A constitutional republic is a form of government that guarantees certain freedoms and limits the power of the central or state governments.
The laws of a constitutional republic are written in a constitution or statutes, and the Supreme Court and the highest courts of all states and territories have the final word. The constitutions establish the basic principles of a government and the relationships among the three branches. The constitutions may be amended by a vote of the people or by an act of Congress.
The fundamental principles of law include judicial review and supremacy of the Constitution and acts of Congress. Court decisions are based on evidence presented by witnesses and the parties to the case and the judgment of the judge or jury. Evidence includes testimonial and physical evidence such as contracts, weapons, and photographs. The judge or jury may consider exculpatory or punitive evidence in making their decision.