On November 7 1973, the U.S. Congress overrode President Nixon’s veto of the war powers bill, which curbed the president’s power to commit armed forces to hostilities abroad without congressional approval.
Richert, Lucas Paul. "Congress overrides Nixons veto on Vietnam War". The Literary Encyclopedia. First published 01 November 2008
[http://www.litencyc.com/php/stopics.php?rec=true&UID=5699, accessed 21 May 2013.]