The Supreme Court is the highest court in the United States and the final judge of what the Constitution means. It hears cases the lower courts cannot settle, and its readings bind every other court, legislature, and official in the country. Its defining power is judicial review: it can refuse to enforce a law it finds unconstitutional, which lets an unelected bench overrule an elected majority. That power is nowhere spelled out in the Constitution's text. It was built up through decisions and accepted over time, and it makes the Court unusually strong for a body with no army and no vote to answer to.
A court with no army and no budget cannot force anyone to obey it. Yet in the United States, nine judges who never face an election can set aside a law that hundreds of elected representatives passed and a president signed. Where did that power come from? The usual answer points to a single case in 1803, but that is too neat. Marbury v. Madison was the first time the Court refused to apply a federal statute, and it supplied the classic argument for why a court may do so. Judicial review did not arrive whole from one opinion, though, and the harder claim, that the Court has the last word over the other branches, hardened only slowly across generations. The strange part is not that judges asserted the power. It is that everyone else came to live by it.