This article records tradition as it has been passed down and reported. Its sources are not yet part of the atlas's verified catalogue.
Nowhere does the United States Constitution say the Supreme Court may strike down a law Congress has passed. The framers seem to have expected the power would exist, but they left it unwritten, and it took until 1803 for the Court to claim it out loud. In Marbury v. Madison, Chief Justice John Marshall's Court declared an act of Congress unconstitutional for the first time, reasoning that a written constitution is meaningless if an ordinary law can override it, and that saying what the law is, including whether a law is even valid, is the essence of judicial power. The ruling gave the judiciary a check the other two branches could not simply out-vote: neither Congress repealing the act nor the President enforcing it could undo a determination that the act had never been valid at all. Judicial review is now treated as one of the three pillars of the American system of checks and balances, alongside the veto and the override, even though the clause that supposedly grants it does not exist.