The concept of ‘transnational armed groups’ has been used increasingly since September 11, 2001 by those who consider the ‘war on terror’ to be an armed conflict and who wish to apply the laws of armed conflict, called international humanitarian law (IHL), to that conflict (rather than human rights domestic legislation and international law on cooperation in criminal matters). In this debate, it is often claimed that IHL, as it stands, is inadequate to cover such a conflict and such ‘transnational armed groups’. This paper discusses, firstly, when IHL applies to transnational armed groups. Concretely, this involves the question of whether, and to what extent, the ‘war’ against Al Qaeda can be classified as an armed conflict. It is argued, that under international humanitarian law, the ‘war on terror’ must be split into different components. In some cases, the law of international armed conflicts applies. In others, the law of non‐international armed conflicts applies. In most situations of the ‘war on terror’, IHL does not apply at all. Secondly, this paper looks at the related issue of what determines the existence of an armed group as an addressee of IHL of non‐international armed conflicts. According to what criteria can Al Qaeda be considered an armed group for the purpose of making IHL applicable? When are members of such a group covered by IHL, even though said group is not fulfilling those identified criteria? Thirdly, the rules of IHL covering an armed conflict between a transnational armed group and a state are summarized, in particular the status and treatment of members of such groups. Most importantly, this paper examines whether and how the existing rules of IHL should or could be adapted to (more) adequately cover transnational armed groups. In this context, few concrete proposals suggesting which rules should be adapted, and in what sense, were found. Nevertheless, as a fourth issue, this paper tries to identify certain areas where the existing IHL of non‐international armed conflicts is not entirely adequate because of the extraterritorial character of the fight against transnational armed groups. Fifth, skepticism is expressed about the possibility of extending IHL and of applying it beyond armed conflicts as currently defined when transnational groups are involved. Sixth, as for the mechanisms of implementation, several proposals are brought forward regarding ways by which respect for existing (or any new rules of) IHL by transnational or any other armed groups can be improved. It is argued, centrally, that if armed groups are addressees of IHL, it is indispensable to involve them in the development and implementation of the rules. Finally, the article explores ways, obstacles, and the risks of developing new rules and mechanisms of IHL specific to armed conflicts with transnational armed groups. The author remains skeptical about the realism and utility of any attempt to develop specific rules for such conflicts.