Perhaps the most important arguments in this area are not doctrinal, historical, or textual, but prudential. In the current strategic context, does it make practical sense to require a joint resolution of Congress before the president can act? For example, with respect to extended deterrence -- the vow to treat an attack on our allies as an attack on ourselves -- I would think the answer is clearly no. A treaty -- which must win the consent of the Senate -- would suffice (as it did in Korea). How about the rescue of American nationals when force is required? Again, my sense is no: that the statutes providing such capabilities, and the extensive hearings about these contingencies which precede the adoption of those statutes by Congress, are sufficient. (This is in accord with the Adams precedent, by the way, which used three acts of Congress that appropriated funds as the basis for prosecuting the war.) What about an attack on a nascent nuclear capability sought by a hostile state? This is more doubtful, but I would be inclined to conclude that the Congress that appropriated funds, after extensive hearings over several years, for "bunker-busting" munitions could hardly claim to have been surprised when those weapons were used in the very contexts discussed at the time of the authorization and appropriations process.
These examples all have in common a certain urgency and the necessity for stealth. When there is time, the prudential calculus changes. Little is lost and much is gained by a fresh congressional debate over Syria, where there are no good tactical options that would be jeopardized by such a debate, and where the public has yet to be satisfied that the administration has good reasons for its decision.
President Obama's situation in some respects resembles that of President George H. W. Bush in the run-up to the first Gulf War. Overruling his national security advisor, Bush went to Congress for a joint resolution authorizing the U.S. invasion of Iraq. It was a daring gamble that the president finessed by announcing that he believed he had the authority to proceed in any case. This tactic seems to have narrowly won the day, with the consequence that -- although the victory in the Senate was razor-thin -- there was eventually broad public support. On Saturday, the president took a roughly similar position, saying, "while I believe I have the authority to carry out this military action without specific congressional authorization, I know that the country will be stronger if we take this course, and our actions will be even more effective."
As to whether the president is correct in his assessment that he does not, as a constitutional matter, need further congressional authorization, I am as yet undecided. The constitutional arguments for presidential intervention in Syria, absent either a North Atlantic Council endorsement or perhaps a vote by the members of the Arab League (for whose security Congress has provided extensive military assistance), are weaker than some recent precedents. In any case, I doubt it matters now. It is most unlikely that the president will use force in the face of an explicit congressional rejection of his request for authorization to use force. He carefully announced on Saturday that he had "decided that the United States should take military action against Syrian regime targets" -- not that he will.
But the really important points are that the president be seen as following the law and that we try to reform the law to reflect the changing strategic context. With regard to the first of these imperatives, I do not believe the president's position will create case law that compromises the powers of the executive any more than the actions of presidents who have reported to Congress "in accordance with" rather than "pursuant to" the War Powers Resolution that they rightly believe to be unconstitutional.
With respect to the second imperative, we must recognize that the 21st-century wars against terror are still fundamentally wars, so far as the rule of law. These wars will be waged in three domains: the campaigns against global, networked terrorists like al Qaeda and their associated allies; the attempt to prevent, and where that is not possible, to mitigate the effects of civilian catastrophes, including genocide, ethnic cleansing, and the mass killing of citizens by their own states; and the struggle to preclude the proliferation of weapons of mass destruction for the purpose of compellance rather than deterrence. President Obama recognized these three arenas when he referred on Saturday to the implications of this crisis for "governments who would choose to build nuclear arms ... terrorists who would spread biological weapons ... armies who carry out genocide."
In Syria, all three of these arenas are in play. And in Syria -- as is the case generally -- progress in one arena often means a worsening of the situation in another. This is the tragic condition of the wars of the 21st century. It may be that a national debate will enable us to appreciate this complexity.