You listed the problem. There are two factions of islam killing one another. They have unlimited funding to buy weapons.

We learned from prohibition, that making something illegal does nothing to stop it. A total arms embargo will not stop the killing. It will simply cost more for the weapons, or force them to use home made chemical or biological ones.

If that doesn't work, they will continue with swords and rocks. They HATE one another, and intend to keep fighting until one side is wiped out.

Then they will begin exporting murder. They are insane.