Wikipedia:
Postol has written about the 2013 Ghouta chemical attack, and he has collaborated with Maram Susli (known online as 'Syrian Girl' or 'PartisanGirl') in examining YouTube footage and other sources. Together they believe they found a number of items to be inconsistent with the conventional narrative of the incident. Together with 'Syrian Girl' and Richard Lloyd, Postol argued that the Ghouta chemical attack did not seem to have been launched by the Syrian government
And yet Assad agreed to turn in his stockpile of chemical weapons.