Marbury v. Madison (1803) Definition

A U.S. Supreme Court decision striking down as unconstitutional part of the Judiciary Act of 1789, on the ground that Congress had impermissibly attempted to expand the Supreme Court's original subject matter jurisdiction.

While Marbury formally was about the constitutionality of a federal statute, it was, in reality, about much more than that. In particular, Chief Justice John Marshall, who wrote Marbury for the Court, wanted to establish the judicial branch as a legitimate and—if it chose to be—a dominant force in American politics.

Marshall did this by effectively announcing that the judiciary has the final say over what laws are constitutional. When there is a conflict between the Constitution and a law passed by Congress, who decides which must prevail? The judicial branch, said Marshall.

"It is emphatically the province and duty of the Judicial Department to say what the law is." Marbury v. Madison, 5 U.S. (1 Cranch) 137, 177 (1803). Because Congress, in the Judiciary Act of 1789, tried to expand the Supreme Court's subject matter jurisdiction beyond what the Constitution allowed, it fell to the Court to declare that part of the Judiciary Act unconstitutional.