Answer:
Marbury v. Madison, legal case in which, on February 24, 1803, the U.S. Supreme Court first declared an act of Congress unconstitutional, thus establishing the doctrine of judicial review.
Step-by-step explanation:
Marbury v. Madison, arguably the most important case in Supreme Court history, was the first U.S. Supreme Court case to apply the principle of "judicial review" -- the power of federal courts to void acts of Congress in conflict with the Constitution.