Marbury v. Madison

On February 24, 1803, the United States Supreme Court first ruled a law unconstitutional (Marbury v Madison). From the article:

"Marbury v. Madison
In Marbury v. Madison (1803) the Supreme Court announced for the first time the principle that a court may declare an act of Congress void if it is inconsistent with the Constitution. William Marbury had been appointed a justice of the peace for the District of Columbia in the final hours of the Adams administration. When James Madison, Thomas Jefferson’s secretary of state, refused to deliver Marbury’s commission, Marbury, joined by three other similarly situated appointees, petitioned for a writ of mandamus compelling delivery of the commissions.

Chief Justice John Marshall, writing for a unanimous Court, denied the petition and refused to issue the writ. Although he found that the petitioners were entitled to their commissions, he held that the Constitution did not give the Supreme Court the power to issue writs of mandamus. Section 13 of the Judiciary Act of 1789 provided that such writs might be issued, but that section of the act was inconsistent with the Constitution and therefore invalid.

Although the immediate effect of the decision was to deny power to the Court, its long-run effect has been to increase the Court’s power by establishing the rule that ‘it is emphatically the province and duty of the judicial department to say what the law is.’ Since Marbury v. Madison the Supreme Court has been the final arbiter of the constitutionality of congressional legislation."