In the space of a single primetime address on [September 10], Barack Obama dealt a crippling blow to a creaking, 40-year old effort to restore legislative primacy to American warmaking. The administration's rationale, at odds with the war it is steadily expanding, is to forestall an endless conflict foisted upon it by a bloodthirsty legislature. Yet one of the main authorities Obama is relying on for avoiding Congress is the 2001 ... document known as the Authorization to Use Military Force (AUMF) that few think actually applies to ISIS. Taken together with the congressional leadership's shrug, Obama has stripped the veneer off a contemporary fact of American national security: presidents make war on their own, and congresses acquiesce. An allergy to congressional authorisation is enmeshed with the president's stated desire to end what he last year termed a perpetual war" footing. It has led Obama in directions legal scholars consider highly questionable. Not only has Obama rejected restrictions of his warmaking power, he has also rejected legislative expansions of it - a more curious choice. Obama has been wary that Congress will offer up new laws that entrench and expand an amorphous war that, in his mind, he has waged with the minimum necessary amount of force. Obama last year advocated the eventual repeal of the 2001 authorisation - as well as the 2002 congressional approval of the Iraq war - to aid in turning a page on a long era of US warfare. [After Obama's address] a senior administration official told reporters that the 2001 authorisation covered the war against ISIS.