I was reading earlier today on the AP newswire a Syrian Kurd stated it wouldn't make sense for Assad to use a chem weapon that close to his stronghold. However, it would make perfect sense for rebels to use it on some civilians and point the finger at Assad. We've been saying for months chemical weapons represented a "red line" and hinted force would be used. He certainly made an interesting point. Ultimately, there is no way of knowing who set off that weapon. None. Without that information, I doubt we won't see more out of the UN than a strongly condemnation. I'm sure both Assad and the rebels will quiver in abject terror when they read it.

If Muslim nations take the lead, it may devolve into a sectarian war. Iran is focused on Western interference at the moment, so other Muslims taking the lead will throw a wrench in that. If Turkey and Saudi Arabia take the lead, I would expect to see the rhetoric change- most likely stop- and Syrian Shi'ite militias with new toys and training. It's not like they don't have decades of experience supporting proxies. I don't think boots-on-the-ground is an option for two reasons:
1. It would be political suicide at home.
2. Getting there is mighty tough with Iraq and Turkey in the way.

Extremists will say whatever Muslim country comes to help the other side is a Puppet of the West, so that's about par for the course.