A Landmark decision, or Landmark court decision, establishes new precedents that establish a significant new legal principle or concept. Or it changes the interpretation of existing law. In Commonwealth countries, a reported decision is said to be a leading decision. This is when it has come to be generally regarded as settling the law of the question involved.[1]
A landmark decision is "a most important case which has establish a law firmly in an area, usually referring to a U.S. Supreme Court case."[2] A landmark decision may have either long-term or short-term significance.[3] Politics, economics or other changes in society may reduce the effects of a landmark decision. A landmark decision is one that changes an entire area of the law during a period of time.[4]
The United States Constitution did not provide for judicial review of laws and court decisions. It was a power the US Supreme court assumed (took) for itself with its first landmark decision.[3] In the decision Marbury v. Madison (1803) the court established its "power to say what the law is". The court gave itself the right to interpret the constitution.[3]