Matthew Yglesias defends his view that the United States ought to obtain UN authorization for any non-defensive use of military force, and that no exceptions can be made for humanitarian crisis, because we never use humanitarian force anyway:
The basic way the conversation goes is basically that whenever humanitarian emergencies break out, we do nothing to stop them. And sometimes we invade Iraq. But then whenever anyone suggests that the U.S. commit itself to following international law and not using non-defensive military force absent a UN Security Council authorization, people show up insisting that we need to maintain the right to unilateral non-defensive war in order to stop genocide. Then whenever humanitarian emergencies break out, we do nothing to stop them. But the larger cause of unilateral militarism lives to fight another day.
But the notion that "whenever humanitarian emergencies break out, we do nothing to stop them" is incorrect. During the Clinton administration, the United States intervened to stop the mass slaughter of Bosnians and then Kosovars. It didn't work perfectly, but it worked, and it would have worked better if we had intervened earlier.
I'd also point out that the notion that the United States can't intervene militarily without U.N. Security Council authorization is not a historical norm that existed before the Bush administration smashed it. In fact it's never existed at all. I explained this in a TNR article five years ago. No government in American history has ever committed itself to gaining U.N. permission before using non-defensive force. (Granted, this only goes back to the founding of the U.N.) Previous governments did pay more attention to international opinion than the Bush administration has, but none of them granted it veto power. The Clinton administration's motto in this regard was "Multilateral when we can, unilateral when we must."
There's nothing in Barack Obama's rhetoric or appointments that suggests he won't follow this same philosophy. Indeed, Hillary Clinton and other key foreign policy actors in his administration believe the Clinton administration's intervention in Bosnia and Kosovo, without UN permission, was one of the highlights of that presidency. Yglesias depicts advocates of non-UN certified humanitarian intervention as as poseurs who are looking for excuses to attack foreigners:
But other people — usually the people with a real interest in humanitarian issues and the crisis-afflicted regions, rather then generic Very Serious People — are talking about actually finding ways to prevent people from being killed, not finding new pretexts for killing people.
There is a school of thought which holds that U.S. intevention in the Balkans was a pretext to kill people rather than a genuine effort to stop genocide. But this school is mostly associated with extreme Serbian nationalism. I'm surprised to see it propounded by an organ of mainstream American liberalism.