Within the context of the controversial issue concerning the legal framework applicable to acts carried out during armed conflict, an authoritative decision of Section I of the Court of Cassation has identified a “hard core” of conduct that may be identified as “terrorist”, relying heavily on the classification of the victims of such armed attacks. Yet the conduct of foreign fighters, which falls into a gray area not entirely covered by case law or legislation, requires interpreting bodies to engage in new hermeneutic efforts to try and disentangle the overlaps between national criminal law, international law and humanitarian law. Against the backdrop of the continuing lack of any regulation of the issue of foreign fighters, comparative analysis of national court decisions thus presents itself as a useful tool for mapping out the emerging guidelines developed in this area by European case law.