The Libyan rebels and the Arab league asked for assistance.  If you want to question the legitimacy of these organizations and the heads of state that provided assistance, then fair enough.  But they are the one who asked, sorry begged for intervention.

Personally, I think Europe should have left them alone to sort out their own mess, and ignored the pleas for the West to play policeman.  Or let China and Russia handle it--they have greater need for the oil and potentially more invested in a stable Libya.