May 2013 UN points the finger at the rebels.
http://rt.com/news/un-syria-rebels-chemical-weapons-854/
UN human rights investigators have spoken to the victims of Syria’s civil war and gathered medical testimonies which point to the Syrian rebels having used sarin nerve gas, while any allegations of its use by the government remain unsubstantiated.
The United Nations independent commission of inquiry on Syria has concluded that no evidence of the use of sarin by Syria’s government troops has so far been uncovered, said the lead commission member Carla Del Ponte on Sunday.
In an interview to Swiss-Italian television, Del Ponte revealed that the “investigators have been in neighboring countries interviewing victims, doctors and field hospitals and, according to their report of last week which I have seen, there are strong, concrete suspicions but not yet incontrovertible proof of the use of sarin gas, from the way the victims were treated.”
That source is Russia & they’re on Assad’s side.
The article does also say:
““The Independent International Commission of Inquiry on the Syrian Arab Republic wishes to clarify that it has not reached conclusive findings as to the use of chemical weapons in Syria by any parties to the conflict. As a result, the Commission is not in a position to further comment on the allegations at this time,” the statement read.”
Not that the MB couldn’t have done it.