The Cliff Notes version, as I’ve heard it, is that there are not only zero doubts that chemical weapons were used, but that the means by which the rebels could have acted out these attacks are virtually impossible. Triangulation of the launch sites indicate they are in loyalist territory, that they utilized weapons that would be time-consuming to use and hard as hell not to see or hear in operation, and would have (most importantly) required the rebels to have a level of training and experience that nobody has been able to find evidence of in their ranks.

At this point, the idea that the rebels were responsible should be something confined to the realm of conspiracy theory.