A state legislature can repeal a corruptly made law, but the Contract Clause of the Constitution prohibits the voiding of valid contracts made under such a law. This was the first case in which the Supreme Court struck down a state law as unconstitutional. Decided March 16, 1810 (argued February 15, 1810). Opinion of the Court: John Marshall → go there Topic: Federalism. Fletcher v. Peck, 10 U.S. 87 (1810), is a landmark United States Supreme Court decision in which the Supreme Court first ruled a state law unconstitutional. The decision created a growing precedent for the sanctity of legal contracts and hinted that Native Americans did not hold complete title to their own lands. Wiki link