Judicial Review

The Constitution does not say in so many words that courts may declare laws unconstitutional. Alexander Hamilton argued in Federalist No. 78 that they must, because a constitution is fundamental law and judges must prefer it to an ordinary statute in conflict with it. Chief Justice John Marshall established the power in Marbury v. Madison in 1803, holding that a provision of the Judiciary Act of 1789 was unconstitutional and that it is emphatically the province and duty of the judicial department to say what the law is.

Judicial review applies to federal statutes, executive actions, and, under Martin v. Hunter's Lessee in 1816 and the Supremacy Clause, state laws and state court rulings on federal questions. Any federal court can exercise it, though the Supreme Court has the final word. Courts use it only in actual cases brought by parties with standing, and they avoid constitutional questions when a case can be decided on narrower grounds. Some questions, such as the conduct of foreign affairs or partisan gerrymandering, are treated as political questions left to the elected branches.

In Cooper v. Aaron in 1958, rejecting Arkansas's resistance to school desegregation, the Court declared its interpretations of the Constitution binding on all officials. Critics across eras, from Thomas Jefferson to modern scholars of left and right, have argued that unelected judges wield too much power over democratic choices, and debates over judicial restraint and activism tend to track which side the Court's majority favors. The power remains the foundation of the judiciary's role as a coequal branch.