The French government released a declassified summary of intelligence tying Assad’s government to the apparent use of chemical weapons, in apparent attempts to strengthen the case for military intervention in Syria.
The intelligence in the summary details alleged proof of the use of chemical weapons, notably Sarin gas, by the Syrian regime and also concluded that opposition forces would not have had the capacity to carry out such large scale chemical attacks.
See here for the full document (in French).
See the New York Times for a summary in English.