Focus . . .
Our focus should be on assistance to Israel, Turkey, Saudi Arabia and Egypt in defeating a shared enemy. This is their backyard, they know the culture, and the Islamic State's (IS) threat toward Western civilization strikes directly at their main interests. The West is where all that tasty, decadent money lies. We should be directing engagements with the local forces (listed above), not blocking them. If they are prepared to strike, even within the sovereignty of Syria, let 'em loose. I have no problem with our allies attacking our enemies.
Pretty cut-n-dried.