Definition of Judicial Review
Judicial review is the process where the courts can review the actions of other branches of the Federal Government and declare their actions unconstitutional. Examples of issues which can be reviewed include laws, treaties, policies or executive orders relevant to cases before the court.
The Supreme Court of the United States spends much, if not most, of its time on hearing cases wherein the constitutionality of a law or regulation is challenged, but experts of the constitution argue the states, in drafting the Constitution, did not delegate such a power to the Supreme Court, or to any branch of the government.
The Supreme Court concreted the practice of judicial review in the landmark case of Marbury v Madison in 1803. According to one source, since this time "the idea that the Supreme Court should be the arbiter of constitutionality issues has become so ingrained that most people incorrectly believe that the Constitution granted this power."