Barack Obama signed off on beginning a war with Libya because the UN had approved it. He was opposed to Iraq because the UN hadn't approved it. Amid all the other explanations he and his administration have been offering, that is the only one that seems to have not yet contradicted itself.
Yes, that is reductionist on my part, the sort of oversimplification and generalisation that should never enter intelligent discourse about complex foreign policy matters. I get that. We know how the game is supposed to be played, with chin-stroking analysis, like art critics marveling over how some pointless drivel raises interesting questions or starts a conversation about what art is supposed to be. But I ask in reply Is it true? Is there anything which contradicts this analysis? What is its disproving evidence?
To the absolutely fair question of what might be offered as evidence for this proposition, I will note that this is precisely what the most fevered of right-wing nutcases predicted: that leftists in general and Obama in specific think the UN, not any individual nation (and certainly not the US during uh, some administrations) is the real constituting authority for war.
So. What other arguments hold up to scrutiny?
Note: I offer no opinion here whether attacking Libya is a good idea. I like it less the more I look at it, but I don't pretend to know enough to give wise analysis.