Originally Posted by C-D-P

http://www.usdoj.gov/olc/warpowers925.htm

"The President has broad constitutional power to take military action in response to the terrorist attacks on the United States on September 11, 2001. Congress has acknowledged this inherent executive power in both the War Powers Resolution and the Joint Resolution passed by Congress on September 14, 2001."

"The President's constitutional power to defend the United States and the lives of its people must be understood in light of the Founders' express intention to create a federal government "cloathed with all the powers requisite to [the] complete execution of its trust." The Federalist No. 23, at 122 (Alexander Hamilton) (Charles R. Kesler ed., 1999)."