Military Commissions are a form of military tribunal convened to try individuals for unlawful conduct associated with war. Though sometimes controversial, they are rooted in U.S. law and in the international laws of war. The term “military commission” first became common in the U.S. during the Mexican-American war. Subsequent practice, legislation, and U.S. Supreme Court precedents have shaped them. Today, a convening authority appointed by Secretary of Defense convenes military commissions under the Military Commissions Act of 2009, passed by the U.S. Congress, and signed into law by President Barack Obama on October 27, 2009.