Neither Obozo nor that pompous fool Lurch will make a 'No retreat' stand against Putin or China, and both of the Russians and Chinese know that. To the extent that they are showing restraint, it's only in the interests of preserving the appearance of diplomacy for the sake of the longer game.
Not that I think Putin is doing the wrong thing in Syria. Our policy is insanely counterproductive. We want to destabilize Assad and choke his ability to fight, but the next-most-powerful player is ISIS which our policy has only empowered. As far as the 'Good' rebels are concerned, they are completely ineffective, the only point where our support might have mattered positively was back in the 'Red line' days (And we know how that went), and now they're nothing but a sideshow. The only recognized government in Syria is Assad's, and Putin was invited in by it; that Syrian government has not acted against us, and therefore I do not see any legitimate basis for the West to claim any superior right to operate in Syria against anything but ISIS-controlled areas. Since ISIS has no air force, the idea of declaring a 'No fly zone' strikes me as something the Russians and Syrians could laugh off, and something for which there is no detectable legal basis in international law.
On top of all that, the 'Forces of democracy' which we are supposedly backing to oust Assad are somewhere between Turkey and the USA, all the military age men we are supposedly supporting in the fight are in the refugee stream, along with thousands of ISIS sleepers and hundreds of thousands of Muslims with just as primitive and barbaric worldviews as the assholes they are running from. People are adaptive, if you give them a choice between leaving for The Land of the Big PX and fighting an oppressive government while eating rocks and dirt, most of them will pick the 'Leave' option. The ones who stay in those circumstances are just as crazy and bloodthirsty as the oppressors they're fighting, they are not more democratic or cuddlier. Throwing open the gates of the West essentially cuts the legs out from under any popular rising that has any chance of ending in democratic government in Syria (The prospect of which I find incredibly dubious to begin with).