(Feb. 24, 1803), landmark U.S. Supreme Court decision, the first instance in which the high court declared an act of Congress unconstitutional, thus establishing the doctrine of judicial review.

The Supreme Court's growing conflict with President Jefferson and the Republican Congress came to a head after Secretary of State Madison, on Jefferson's orders, withheld from William Marbury the commission of his appointment (March 2, 1801), by former President Adams, as justice of the peace in the District of Columbia. Marbury—one of the so-called “midnight appointments” made in the final hours of Adams's term under the Judiciary Act of 1801—requested the Supreme Court to issue a writ of mandamus compelling Madison to deliver his commission. In denying his request, the Court held that it lacked jurisdiction because Section 13 of the Judiciary Act passed by Congress in 1789, which authorized the Court to issue such a writ, was unconstitutional and thus invalid. Chief Justice Marshall declared that in any such conflict between the Constitution and a law passed by Congress, the Constitution must always take precedence. The apparent “victory” for Jefferson was in fact a landmark in asserting the power of the Supreme Court's life-tenured justices, which Jefferson hated and feared.