Modern Warfare

 GW: "The case against the rebels using chemical weapons is generally poor, with a variety of
unsubstantiated claims and circumstantial evidence. Often clinical
signs and symptoms are missing. The one exception to this seems to be Khan
Al Asal. What did you find that lifted it out of the rest?"

  AS: "Regarding the first issue [opposition CWA attacks], I fully agree. Several times I asked the government: can you explain — if this was the opposition –– how did they get hold of the chemical weapons? They have quite poor theories: they talk about smuggling through Turkey, labs in Iraq and I asked them, pointedly, what about your own stores, have your own stores being stripped of anything, have you dropped a bomb that has been claimed, bombs that can be recovered by the opposition? 

 They denied that. To me it is strange. If they really want to blame the opposition they should have a good story as to how they got hold of the munitions, and they didn’t take the chance to deliver that story."

 Even on Khan al-Asal, it is as feasible that the government thought it could fabricate evidence for that attack being by the opposition, just as they claimed to have footage showing the tunnels through which the rebels brought the chemicals used in the August attack. Via here*, where there is a shorter version.
*[http://eaworldview.com/…/syria-carried-chemical-weapons-at…/]