This Master s thesis seeks to promote a possible post-foundational philosophical investigation on the reconstructions of the relation between legitimacy and legality by International Relations (IR), in specific juxtapositions with the field of International Law (IL). This research is especially motivated by those context and discourse that sought to reconstitute this relation in terms of differentiation (e.g. illegal, yet legitimate) or potential similarity (e.g. illegitimate but legitimate, albeit quasi-legal) between the two concepts/entities, such as the attempts to epistemically and politically order the events concerning the North Atlantic Treaty Organization (NATO) s use of force in Kosovo in 1998-1999. Throughout this piece, this postfoundationalist theoretical-philosophical perspective takes on different facets, transdisciplinaryly moving around the fields of Philosophy (Ludwig Wittgenstein e Jacques Derrida), International Relations (constructivism, post-structuralism, and post-colonialism) and, occasionally, International Law (critical legal studies) and Sociology of Knowledge (ethnomethodology), while seeking to displace the expectations on the ontological character of legitimacy and legality - i.e. the understanding of them as meaningful concepts/entities in themselves which are intertwined with strategies of epistemic ordering and circumscription of political imagination - and thus to reconstruct (and not to reject) the knowledge and politics of the legitimacy/ legality in IR. This work particularly investigates a possible sociological form of reflection that is politically engaged with this relation, that is, a form of epistemic-political engagement in which the suspension of the meaning of the legitimate and/or the legal constitutes a key moment for a political opening towards a continuing investigative sensibility vis-à-vis the limits that have been designed by the attempts to delimit a right-being of the world; which is in turn limitedly mobilized as a contingent sociological impression through the contextual and discursive performance of a normative judgement attached to the legitimacy/legality relation.