There is no such imperative, argues Sheldon Richman here.
My hunch is that Obama knows that nothing the United States can do will have any good effect in Syria, but because the public has been so imbued with the idea that the president must act whenever there is any problem, foreign or domestic, it has become impossible for POTUS (any POTUS, present and future) to speak these words, “It is none of our business.”
