Just War Criteria:
1. Just Cause
This is always tricky to decide subjectively, but as Walzer argues, you must observe political autonomy and respect international borders as those embroiled in civil/secessionist conflict need to maintain a balance. If the US or NATO were to intervene and this tipped the scales in favor of the rebels, if they won decisively because of our entrance, then this would fail this criteria. Seems strange that this is so rigid but nonetheless it fails.
This one is easier to satisfy. First, the intervention (no fly zone) must be done by a recognized world government. Check. Next it must have international approval. This has been danced around so far, the UN has not determined anything as of yet, perhaps looking at points made in this doctrine. Also China and Russia typically veto anything they see as meddling in other countries internal affairs.
Another sticky point. It is impossible to say that the US intervening would be to strictly balance the sides and done simply in the interest of the oppressed party. Sure, that could be part of the argument but why do we care about Libya in the first place? Oil is one, and having a favorable government installed would allow more influence in the region. Sadly its nearly to truly meet this condition, although if a true humanitarian crisis arose, where the world was convinced of great threatening evil to all Libyan people (and maybe surrounding countries), the intention would be good and therefore just. It just needs this disinction.
4. Probability of Success
This one is pretty sure. US air power is vastly superior to what Gaddafi has. Success is realistic and therefore satisfactory.
We are moving closer to meeting this goal. We have already taken indirect and diplomatic measures to help put pressure on Gaddafi. Its impossible to tell if you are really on "the last resort" but if the situation because dire in a humanitarian way as mentioned above, this would be met.
This is most likely appeased. By intervening, we would eliminate Gaddafi's air power, and we would have to stop there. That is what the rebels asked and that would restore "balance." Introducing land war would over step this boundary, that is, unless another power comes to the help of the loyalists in which case Just War states that counter-intervention is just and nearly necessary. Gaddafi's influx of mercenaries could be defined as foreign help, but again this is ambiguous and requires deeper analysis.
The US has the technology to make civilian casualties limited but not extinct. The F-22 has the ability to evade Libya's ground-to-air defenses that would need to be bombed otherwise, and cause noncombatant deaths. Therefore we can meet this criteria from a teleological argument.
Overall it seems that a no-fly zone misses some points that are required to make the intervention "just" but should the conflict degenerate into a genocide or mass executions break out, it would alleviate some of the constraints that formally held back the move, and indeed may call for a more of a response. Also, we need to weigh the fact that bringing in multiple aircraft carriers would take away from our other conflict (Afghanistan, Iraq) and would also become quite costly; not something that wants to be brought up in the middle of a budget crisis.