In 1803, the Supreme Court handed down its unanimous ruling in Marbury v. Madison. The facts of the case involved William Marbury, who was appointed to a government position by President John Adams, about to yield the presidency to Thomas Jefferson. Marbury never physically received his appointment letter, and appealed to the Court. Marbury was owed his commission, Chief Justice John Marshall ruled.

His opinion took a turn, though, when he announced that the Supreme Court was actually unable to provide Marbury with his remedy. Marshall, reasoning that “It is emphatically the province and duty of the Judicial Department to say what the law is,” announced that the Judiciary Act of 1789, which allowed the Court to hear cases such as Marbury’s, was unconstitutional. With this pronouncement, Marshall avoided a political showdown with the Jefferson administration and established the principle of judicial review—that the Court could determine whether or not a law was constitutional. Considered perhaps the most important case in the development of the Supreme Court, Marbury v. Madison solidified the third branch, the judiciary, as coequal with the legislature and the executive.