Which term refers to the authority of courts to declare a law unconstitutional?

The term that refers to the authority of courts to declare a law unconstitutional is judicial review. This principle is a foundational aspect of the legal framework in many democracies, allowing the judiciary to ensure that legislative and executive actions comply with the constitution. Judicial review serves as a check on the powers of the other branches of government, giving the courts the ability to protect individual rights and uphold the rule of law.

For example, in the landmark case of Marbury v. Madison in 1803, the United States Supreme Court established the practice of judicial review by declaring an act of Congress unconstitutional, thereby affirming the power of the judiciary to interpret the law and its relationship with the constitution. This function is crucial in maintaining a balance of power among the government branches and ensuring that any laws passed do not violate constitutional principles.