Statutes are the laws passed by elected federal, state, and local legislatures. Administrative rules and regulations are the rules issued by regulatory agencies. For example, the Internal Revenue Service develops the rules that specify how people should comply with the tax laws passed by the U.S. Congress. Case law, also known as common law, is the law created by judges when deciding individual disputes or cases. Though each judicial opinion is intended to resolve only the particular case before the court, the way judges interpret and the apply the law in each case serves as a precedent for courts facing similar cases in the future and is usually considered binding on that court and all lower courts in the same jurisdiction.
Courts sometimes do, however, overrule their own precedents.
When a novel legal question comes before a court, it is called a case of first impression. Common law is derived from the English judicial system, in which there were few statutes at first and judges decided disputes based on social custom and on what they thought was fair. Once made, a decision became the precedent for all similar cases to follow. In our country, judges are guided by the laws passed by Congress and the state legislatures, and judicial decisions are often interpretations of those laws. If no statute specifically governs a dispute, previous judicial decisions are relied on.