I’m a little curious why no one here seems to have mentioned UN Security Council Resolution 1973. This resolution seems to be used as a strong reference when governments of participating states explain Operation Unified Protector. I also get the impression that the resolution provides a legal basis which is different from e.g. Operation Iraqi Freedom.
I guess that the behaviour of the Gaddafi government, the calls for assistance from the opposition in Libya and the reactions from some Arab states are among the things which have contributed to the passing of the resolution and the international resolve to enforce it.

Some European politicans have said something along the line of that they feel it is important to back up UN decisions with military force when called for/when necessary. A spoken reason for this is to strengthen the UN as an important political body in the world.

Personally I support Unified Protector, but I do have some concerns about the future of Libya. Who the rebels are, what will they do if Gaddafi falls, how will all of this affect al-Qaeda’s activities in the region (as well as other groups which might be of interest), what if a stalemate lasts etc.

When it comes to the possibility of “less visible” agendas which some people claim exist in this, I mostly think it’s speculation. Even if some participating states hope to serve some of their own interests by engaging in the operation, it still seems to me that the military effort helps enforce the UN resolution correctly by reducing Gaddafi’s military capacity to threaten civilians.

I should of course take some precautions since I can’t possibly know everything, but right now I think the operation seems just (though I’m sure some things can be done better).