This article addresses the question of the lawfulness under international law of the use of force to implement the part of the UN Security Council Resolution 1973 (2011) establishing a no-fly zone (NFZ) over Libya. This question, so far neglected by the doctrine, raises thorny legal issues as the legal contours of a NFZ are not settled. According to available information, it will be demonstrated that the intervention of the States acting individually or within NATO to enforce the NFZ over Libya comes under scrutiny mainly in relation to the lawfulness of the use of force with respect to air-to-ground attacks, as it is dubious that a NFZ allows strikes against ground targets. In the article it is argued that, even admitting that such strikes are permitted, the relevant legal criteria that emerge from the combination of the jus in bello and jus ad bellum rules have to be respected. In particular, according to the interplay between these two branches of the law, only those objects (including aircraft) being used, or intended to be used to attack or threaten civilians could be lawfully targeted.