There appears to be much evidence that it was in fact the rebels that used the chemical weapons which were supplied by the Saudis,
1) Video evidence of Chemical weapons being launched.
2) Photographic evidence of the weapons being Saudi.
3) Testimony from Syrian rebels from the faction that had the weapons and admitted they didn't know what they were doing with them.
And anyway, what is American Military going to do, team up with Al Qaeda and Hezbollah to attack Syria and kill hundreds of thousands more people in the middle east?