Assad is effectively dead meat. He would never have used gas were that not the case. Now, with Russia pressuring him to give up the chemical weapons, he has a major problem. If he gives them all up, he is going to lose big time. However, if he saves some back, and uses them, the Russians have the option of abandoning him and seeking favor with some faction of the rebels.
This is not the kind of situation that has nice clean clear cut black and white choices. Like most of the decisions concerning the Middle East, it is a choice between bad and really bad. Whatever we can do to aid in removing Assad without putting our boots on the ground, or having to use military force, is a victory. Like in Libya, what the people of Syria then do with the oppertunity presented them, is their business and problem. However it turns out, the onus is on them, not us. Not at all the situation that we were put into in Iraq.