So...Let me try to understand the logic here: Assad would never gas his opponents because that would mean confrontation with Washington and Paris. He was framed. (Unless, of course, he thinks that's what we would think).
But this is all sheer nonsense.
Comrade Assad is fighting for his life, in a brutal civil war. He is the last of the three Baathist dictators standing. The other two - Saddam and Qaddafi - died in a manner that leaves very little room for wishful thinking - or for any ten-steps-ahead strategy games. This is not a party of chess. This is about survival: there will be no legal rigmarole, like with Mubarak, or Pinochet, or even Todor bleeping Zhivkov - not all crimes are created equal, and Bashar knows exactly where his Daddy's regime sits, in the spectrum of the 20th century tyrannies.
Put yourself into the shoes of the thug: What do you have to lose? You absolutely have to inflict the maximum damage possible onto your opponents, NOW. By any means available.
What happens later - who knows? Did the world unite to overthrow Saddam after he - undeniably and openly - gassed the Kurds? Eh, not exactly.
Will your milk brothers, mighty Comrades Pu and Xi save the day? Maybe. Maybe not.
It is a gamble, sure. But in a knife fight, you don't theorize about what may happen half an hour from now. You block the other guy's moves, as effectively as you can.