Judicial Review

The principle that allows the Supreme Court to strike down laws and government actions that conflict with the Constitution

It is emphatically the duty of the Judicial Department to say what the law is.
Chief Justice John Marshall, Marbury v. Madison (1803)
If courts are to regard the Constitution, and the Constitution is superior to any ordinary act of the legislature, the Constitution, and not such ordinary act, must govern the case to which they both apply.
Chief Justice John Marshall, Marbury v. Madison (1803)