the Judiciary Act of 1789 enabling Marbury to bring his claim to the Supreme Court was itself unconstitutional, since it purported to extend the Court's original jurisdiction beyond that which Article III, Section 2, established.

Marshall expanded that a writ of mandamus was the proper way to seek a remedy, but concluded the Court could not issue it. Marshall reasoned that the Judiciary Act of 1789 conflicted with the Constitution. Congress did not have power to modify the Constitution through regular legislation because Supremacy Clause places the Constitution before the

laws. In so holding, Marshall established the principle of judicial review, i.e., the power to declare d law unconstitutional.