QUOTE(amy @ Jan 18 2007, 09:55 AM)

What's the legal reasoning behind them regarding it as unconstitutional? Do you have solid evidence to back up your statement? I believe only Congress has the constitutional authority to take us to war. It is true that Congress's passage of the IWR gave that authority to the POTUS. I also believe the 1973 War Powers Resolution might be unconstitutional, but only because it hands over a constitutional authority of the Congress to the POTUS. Of particular concern to me is the language in Section 2 © 3.
PURPOSE AND POLICY
SEC. 2. (a) It is the purpose of this joint resolution to fulfill the intent of the framers of the Constitution of the United States and insure that the collective judgement of both the Congress and the President will apply to the introduction of United States Armed Forces into hostilities, or into situations where imminent involvement in hostilities is clearly indicated by the circumstances, and to the continued use of such forces in hostilities or in such situations.
(b)Under article I, section 8, of the Constitution, it is specifically provided that the Congress shall have the power to make all laws necessary and proper for carrying into execution, not only its own powers but also all other powers vested by the Constitution in the Government of the United States, or in any department or officer thereof.
© The constitutional powers of the President as Commander-in-Chief to introduce United States Armed Forces into hostilities, or into situations where imminent involvement in hostilities is clearly indicated by the circumstances, are exercised only pursuant to (1) a declaration of war, (2) specific statutory authorization, or (3) a national emergency created by attack upon the United States, its territories or possessions, or its armed forces.
So, if there is a national emergency such as we saw on 9/11, the language seems to imply the POTUS can intorduce the Armed Forces into hostilities without statutory authorization from Congress. Once the military is involved in hostilities we know how difficult it is for Congress to make "course corrections" through the cutting of funds or in any way. Not a good thing, IMO.
One argument for the unconstitutionality of the War Powers Resolution — Philip Bobbitt's in "War Powers: An Essay on John Hart Ely's War and Responsibility: Constitutional Lessons of Vietnam and Its Aftermath," Michigan Law Quarterly 92, no. 6 (May 1994): 1364–1400 — runs as follows: "The power to
make war is not an enumerated power" and the notion that to "declare" war is to "commence" war is a "contemporary textual preconception"; the Framers of the Constitution believed that statutory authorization was the route by which the United States would be committed to war, and that 'declaration' was meant for only total wars, as shown by the history of the Quasi-War with France (1798–1800); in general, constitutional powers are not so much separated as "linked and sequenced"; Congress's control over the armed forces is "structured" by appropriation, while the president commands; thus the act of declaring war should not be fetishized. (Bobbitt, the nephew of Lyndon Johnson, also argues that "A democracy cannot… tolerate secret policies" because they undermine the legitimacy of governmental action.)
A second constitutionality argument concerns a possible breach of the 'separation of powers' doctrine. The legislature may be impeding the executive in carrying-out the Oath of Office. "I do solemnly swear (or affirm) that I will faithfully execute the Office of President of the United States, and will to the best of my ability; preserve, protect, and defend the Constitution of the United States." (US Constitution, Article 2, Section 1, Clause 8) This type of constitutional controversy is similar to one that occurred under President Andrew Johnson with the Tenure of Office Act (1867). In that instance, the Legislative branch attempted to control the removal of Executive branch officers.
Thirdly, Congress is trying to grant it's self the power of a legislative veto over the rights and powers granted to the executive branch in the Constitution.
If the Supreme Court ever set it's teeth into the War Poweers Act it would be out the window PDQ.
If you want to read a thorough analysis here's and article prepared by an academian at the Air Force War College.
http://www.au.af.mil/au/awc/awcgate/crs/rl32267.htm#_1_12