Obama, as senator and presidential candidate, made the serial argument that U.S. military interventions, barring an “imminent threat” to our national security, are both illegal and immoral unless they have the triad of U.S. congressional support, U.N. approval, and American public support.
In the present circumstances, to make the argument for attacking Syria he must assume that congressional authorization is an eleventh-hour afterthought and not necessarily binding, that the U.N. is mostly hocus-pocus and not worth the bother, and that overwhelming public opposition does not matter.
There are so many contradictions and hypocrisies in such thinking as to render it farcical. I’ll give one, though: In 2002–03 George Bush built public opinion for an intervention, assembled an allied coalition, succeeded with the U.S. Congress, and tried at the U.N. He made the argument that Saddam Hussein’s past use of WMD, his support for terrorism, and his genocide (read all 23 congressional writs) made a good moral and realist case for intervening in a post-9/11 landscape. In response, Barack Obama launched his political career by deriding just such logic, which he is now far less impressively adopting as his own.