The central figure in the Marbury v. Madison Supreme Court case was William Marbury. In 1803, Marbury petitioned the Supreme Court to compel Secretary of State James Madison to deliver his commission as a justice of the peace, which had been withheld. The case, presided over by Chief Justice John Marshall, led to a landmark ruling that established the principle of judicial review, meaning that the Supreme Court could overturn laws deemed unconstitutional. This decision greatly expanded the role and power of the judiciary in American government and solidified its position as a co-equal branch alongside the executive and legislative.