Over on my Facebook page there’s a bit of a discussion going about then-Senator Barack Obama’s statement that “The President does not have power under the Constitution to unilaterally authorize a military attack in a situation that does not involve stopping an actual or imminent threat to the nation.”
Given what’s happening in Libya, that’s obviously a form of hypocrisy you can believe in. Then again, it’s not particularly surprising hypocrisy. From Harry Truman on, all presidents have in practice asserted the power to authorize military without congressional approval and I never for a moment believed that Barack Obama would abandon this practice if he became president.* The fact that the constitution seems to clearly rule this out hasn’t been a barrier to anyone’s practical conduct for decades. But the one observation I would make about this, is that while the trend toward undeclared military incursions is often described as a kind of presidential “power grab” it’s much more accurately described as a congressional abdication of responsibility. Even if you completely leave the declaration of war business aside, congress’ control over the purse strings still gives a determined congressional majority ample latitude to restrain presidential foreign policy. The main reason congress tends, in practice, not to use this authority is that congress rarely wants to. Congressional Democrats didn’t block the “surge” in Iraq, congressional Republicans didn’t block the air war in Kosovo, etc. And for congress, it’s quite convenient to be able to duck these issues. Handling Libya this way means that those members of congress who want to go on cable and complain about the president’s conduct are free to do so, but those who don’t want to talk about Libya can say nothing or stay vague. Nobody’s forced to take a vote that may look bad in retrospect, and nobody in congress needs to take responsibility for the success or failure of the mission. If things work out well in Libya, John McCain will say he presciently urged the White House to act. If things work out poorly in Libya, McCain will say he consistently criticized the White House’s fecklessness. Nobody needs to face a binary “I endorse what Obama’s doing / I oppose what Obama’s doing” choice.
Which is all just to say that presidents will go back to accepting congressional authorization for the use of force as a binding constraint when congress starts actually wanting that authority.
I also think you could offer a lawyerly defense here wiggle around the word “unilaterally.” You could say that this is a very multilateral operation conducted by NATO under legal authorization from the United National Security Council and that congress de facto authorized it by assenting to the North Atlantic Treaty and the UN Charter. But the trend is toward all postwar presidents asserting broad “commander in chief” powers and Obama’s no exception.