Judicial review

From dKosopedia

When a court exercises its power to determine if legislation is legally enacted, usually as a result of a conflict with the United States Constitution, a federal law and a state law, or a state constitution, this is called judicial review, which is a major innovation of the American legal system.

Prior to the United States Constitution, courts simply assumes that all laws enacted were valid and lacked the power to invalidate them (a natural conclusion in th British system where the constitution is unwritten and all political power flows from the sovereign through parliament).

Many countries in Europe reserve the power of judicial review to special constitutional courts, but in the United States, it is a power held by almost every judge right down to the lowly magistrate (subject, of course, to review on appeal).