Declaration of War - United States

United States

In the United States, Congress, which makes the rules for the military, has the power under the constitution to "declare war". However neither the U.S. Constitution nor the law stipulate what format a declaration of war must take. War declarations have the force of law and are intended to be executed by the President as "commander in chief" of the armed forces. The last time Congress passed joint resolutions saying that a "state of war" existed was on 5 June 1942, when the U.S. declared war on Bulgaria, Hungary, and Rumania. Since then, the U.S. has used the term "authorization to use military force", as in the case against Iraq in 2003.

Sometimes decisions for military engagements were made by US presidents, without formal approval by Congress, based on UN Security Council resolutions that do not expressly declare the UN or its members to be at war. Part of the justification for the United States invasion of Panama was to capture Manuel Noriega (as a prisoner of war) because he was declared a criminal rather than a belligerent.

In response to the attacks on 11 September 2001, the United States Congress passed the joint resolution Authorization for Use of Military Force Against Terrorists on 14 September 2001, which authorized the US President to fight the War on Terror.