This article analyses legitimation processes of nato’s member military intervention over Libya in 2011. By using Foucault’s methodological tools for discourse analysis, our aim is to study discursive structures in which the justifications of the operation were inserted. Thus, by displacing our analytical focal from argument contents to their organization in discursive structures, we suppose that the legitimation of the intervention did not rely on precise and delimited arguments, but on a network of moving and interdependent justifications.