Ground based air defenses can't really deny control of the air to the enemy. How good are they at doing this? Well, less than 1 in 50 SAMs launched against NATO aircraft in the Balkans actually hit. SAM/AAA distract and attrit but have rarely ever substituted for interceptors. And most of Libya's good SAMs are concentrated around Tripoli.
Besides, even if the Arab League only flew CAP over rebel territory this would help a lot.
Yep, Hillary or Bill Clinton spoke about this -- Establishing a no-fly zone would have to entail ground assaults against such installations, and then you've gone against the rebels' demands of no foreign troops on Libyan soil, in which case why not just get directly involved if you're gonna go that far?
If Hillary said that she's just being Obama's lapdog and justifying US nonintervention. You don't need ground assaults to take out SAMs, anti-radiation missiles launched from aircraft (HARM, ALARM, Kh-31, etc.) are designed specifically to deal with them.
Clinton said we needed ground assaults to take out SAM and radar sites? Urgh.

I agree with you there.
I don't personally think the Arab league have pilots trained or well experienced enough to pull off the job most efficiently, though. The Saudi Air Force, for instance, is notoriously bad worldwide (about the closest thing you can get to a corrupt air force, where a Flight Lieutenant can just drop money in someone's pockets and take his family with him in the aircraft). The Jordanian and Egyptian Air Forces might stand a chance through sheer numbers, but I think a lot more general duties officers are going to pay the price than necessary.
Air Forces like the British, American, French, Dutch, and Australian train, and in some cases have experience with these kinds of operations far more than the Arab nations do.
I won't say anything about stopping the Arab League trying to enforce something, but I think we should be prepared for more losses than we're used to expecting from our own Air Forces.
EDIT: Spelling.