"The last time anyone tried to repeal the Iraq AUMF was November 29, 2011, when Rand Paul's effort failed 67 to 30 with three members abstaining. That's a staggering margin for keeping the war going."
http://www.theatlantic.com/politics/archive/2013/05/zombie-iraq-war-why-havent-we-repealed-the-authorization-to-fight-there/276315/