Summary: William Marbury was appointed a justice for the peace for D.C., and James Madison, the Secretary of State under Adams, refused to give Marbury commission. So Marbury and three others in a similar situation petitioned for a writ of mandamus for the delivery of commissions. Chief Justice Marshall denied the petition with a unanimous vote. He said that the Constitution did not give them power to write writs of mandamus. Although the effect of the decision was to deny power to the Court, it actually enforced the idea that the Court decides what the rules are. After Marbury v. Madison, the Supreme Court has had the final say in congressional legislation.
Constitutional ideas involved: The Supreme Court has been the final mediator of the constitutionality of congressional legislation.
Concept that came out of the ruling: The Supreme Court can deem acts of Congress unconstitutional.