The landmark decision in Marbury v. Madison in 1803 established the principle of judicial review in the United States. This case arose when William Marbury petitioned the Supreme Court for a writ of mandamus to compel Secretary of State James Madison to deliver his commission as a justice of the peace. Chief Justice John Marshall ruled that while Marbury had a right to his commission, the Court could not legally compel Madison to act, as the law that enabled Marbury's claim was unconstitutional. This decision asserted the Supreme Court's authority to invalidate laws that conflict with the Constitution, solidifying its role as a co-equal branch of government.