What principle allows the Supreme Court to declare laws unconstitutional?

The principle that allows the Supreme Court to declare laws unconstitutional is judicial review. This authority was established in the landmark case Marbury v. Madison in 1803, where Chief Justice John Marshall articulated the role of the judiciary in reviewing the actions of the legislative and executive branches to ensure they comply with the Constitution. Judicial review serves as a check on the powers of Congress and the president, allowing the courts to uphold the Constitution as the supreme law of the land.

Judicial review is critical in maintaining the balance of power within the government. It emphasizes the judiciary's role in interpreting the law and protecting individual rights against any potential government overreach. By having this power, the Supreme Court can strike down laws or executive actions that it finds violate constitutional principles, thereby reinforcing the rule of law and the foundational structure of American democracy. This mechanism is essential for ensuring that no law or action can supersede the Constitution, maintaining the integrity of the nation's legal framework.