IHL Does Authorise Detention in NIAC: What the Sceptics Get Wrong

As Serdar Mohammed v Ministry of Defence hits the English Court of Appeal, the blogs have lit up with comments, criticisms and predictions. In recent posts published at Just Security and Opinio Juris, Ryan Goodman, Kevin Jon Heller and Jonathan Horowitz (see here, here and here) have joined with Marko Milanovic and Lawrence Cawthorne-Hill and Dapo Akande (see here, here and here) in defending the view that IHL does not provide States with a legal authority to detain persons in a non-international armed conflict (NIAC). In this post, we wish to outline our challenge to this proposition as mistaken in law and undesirable as a matter of policy (for a more detailed version of our argument, see our recent article in International Law Studies here).

The nature of the law of war

In Serdar Mohammed, Mr Justice Leggatt relied on five arguments to deny the existence of a legal authority to detain under IHL in NIACs (paras 228–251). Despite his meticulous analysis, we do not find the reasoning persuasive. None of the five arguments exclude the possibility that a legal basis for detention exists under customary international law. Even if correct, they establish only the absence of an implicit legal basis under Common Article 3 (CA3) of the Geneva Conventions of 1949 and the relevant provisions of Additional Protocol II of 1977 (AP II). However, Leggatt J’s reading of these provisions is too narrow. In particular, it misconstrues the nature and purpose of IHL as a body of law.

According to Leggatt J, the purely humanitarian purpose pursued by CA3 and AP II is inconsistent with the idea that they were designed to confer a legal power of detention (para. 244). Although humanitarian imperatives have played a central role in the development of modern IHL, they have never been its sole preoccupation. Its other purpose has always been the regulation of hostilities. Focusing on the humanitarian aspects of IHL at the expense of its warfighting dimension ignores its fundamentally dual character. In particular, it fails to appreciate the role played by the principle of military necessity. As Nils Melzer has explained, the ‘aim of military necessity as a principle of law has always been to provide a realistic standard of conduct by permitting those measures of warfare that are reasonably required for the effective conduct of hostilities, while at the same time prohibiting the infliction of unnecessary suffering, injury and destruction’ (Melzer, Targeted Killing in International Law, 279–280). The principle therefore serves both a restrictive and a permissive function. The permissive function was expressed by the United States Military Tribunal at Nuremberg in the Hostages Case as follows:

“Military necessity permits a belligerent, subject to the laws of war, to apply any amount and kind of force to compel the complete submission of the enemy with the least possible expenditure of time, life, and money. In general, it sanctions measures by an occupant necessary to protect the safety of his forces and to facilitate the success of his operations. It permits the destruction of life of armed enemies and other persons whose destruction is incidentally unavoidable by the armed conflicts of the war; it allows the capturing of armed enemies and others of peculiar danger.” [page 66]

As a general principle of law, military necessity it is not sufficiently precise to provide detailed guidance on what are permissible aims, means and methods of warfare, and what are not. Rather, it falls to the positive rules of IHL, as laid down in the applicable treaties and embodied in customary international law, to provide that guidance and thereby give military necessity concrete meaning. Military necessity thus feeds into the creation of positive rules as a permissive principle. Take the duty of distinction, for example. By stipulating that attacks may only be directed against military objectives, IHL gives effect to humanitarian imperatives through shielding civilians and civilian objects from hostilities. However, in the same breath, it also recognizes that the use of combat power against combatants and military objects is permissible on the basis of their status as military objectives. This permissive element of the duty of distinction is confirmed by the longstanding, consistent and general practice of States of exercising their liberty to conduct status-based operations against enemy military objectives within the limits laid down by IHL. Contrary to Leggatt J’s ruling, status-based detention is therefore perfectly compatible with the humanitarian aspirations of IHL.

But what about NIAC?

While it is generally (though not universally: see Professor Goodman’s post) admitted that these considerations apply in international armed conflicts, it is debated whether they also apply in NIACs. In fact, they do. Although neither CA3 nor AP II confers an explicit right on States to attack insurgent fighters and civilians directly participating in hostilities, their language nevertheless suggests that such an authority was implied. First, AP II distinguishes between ‘persons’ who benefit from fundamental guarantees under Article 4 and ‘civilians’ who enjoy general protection against the dangers arising from military operations under Article 13. Since the concept of a ‘person’ is broader than the concept of a ‘civilian’, the natural meaning of these words suggests that ‘persons’ include civilians and non-civilians, that is, fighters. Second, Article 4(1) affords fundamental guarantees to two groups: ‘persons who do not take a direct part’ in hostilities and persons ‘who have ceased to take part in hostilities.’ The first group can only refer to innocent civilians who have not taken up arms since fighters by definition take a direct part in hostilities. The second group must therefore logically refer to civilians who have ceased to take a direct part in hostilities and to fighters who are hors de combat. Two points follow from this. Insurgent fighters are not civilians and do not become civilians upon ceasing to take part in hostilities; otherwise the word ‘persons’ would not have been used in preference of ‘civilians’. Fighters do not benefit from fundamental guarantees unless they have ceased to take part in hostilities by becoming hors de combat. In this respect, AP II mirrors the treatment of combatants in international armed conflict (this reading of the text is fully borne out by the drafting history of AP II: see here at footnote 181).

Even if this textual interpretation is not considered conclusive, it is hardly conceivable, reading the relevant provisions against their context, that the drafters of CA3 and AP II meant to treat everyone in a NIAC as a civilian and did not foresee the status-based targeting of insurgent fighters. As the commentary on CA3 notes, ‘it must be recognized that the conflicts referred to in Article 3 are armed conflicts, with armed forces on either side engaged in hostilities—conflicts, in short, which are in many respects similar to an international war, but take place within the confines of a single country.’ Similarly, in the La Tablada case, the Inter-American Commission on Human Rights recognized that:

 “when civilians, such as those who attacked the Tablada base, assume the role of combatants by directly taking part in fighting, whether singly or as a member of a group, they thereby become legitimate military targets. As such, they are subject to direct individualized attack to the same extent as combatants. . . . When they attacked the La Tablada base, those persons involved clearly assumed the risk of a military response by the State.” [paras 178–179]

Meanwhile, the principal rules of IHL governing targeting in international armed conflicts have passed into customary international law so as to now govern targeting in NIACs. Underlying this development is, first, the notion that members of organized armed groups and civilians directly participating in hostilities are fighters and, second, that such persons constitute legitimate military objectives. In line with the principle of distinction, attacks may only be directed against such persons. As the Interpretive Guidance on the Notion of Direct Participation in Hostilities under International Humanitarian Law issued by the International Committee of the Red Cross illustrates, the interplay between humanity and military necessity channels the use of lethal force in the same way in NIACs as it does in international armed conflicts: it shelters civilians and those who are hors de combat from the adverse effects of war and permits States to conduct attacks against combatants/fighters and civilians directly participating in hostilities. The case law of the European Court of Human Rights confirms this conclusion. In Korbely, the Court accepted that, from the perspective of CA3, the leader of an armed group of insurgents who has not laid down his arms or otherwise expressed his clear intention to surrender must be considered as taking an active part in hostilities and therefore constitutes a combatant subject to attack. 

So what about status-based detention?

 The preceding points establish that States enjoy the legal authority under CA3, AP II and customary international law to conduct status-based targeting in NIACs. This is critical in the present context, since the UK Government relied on this authority to argue that ‘the ability to detain insurgents, whilst hostilities are ongoing, is an essential corollary of the authorisation to kill them’ (Serdar Mohammed, para. 252). Leggatt J rejected this argument for the following reason:

“This argument justifies the capture of a person who may lawfully be killed. But it does not go further than that. It therefore does not begin to justify the detention policy operated by the UK in Afghanistan. In terms of the present case, the argument would justify the arrest of [Mr Mohammed] on the assumed facts, in circumstances where he was believed to represent an imminent threat. However, as soon as he had been detained and the use of lethal force against him could not be justified, the argument no longer provides a basis for his detention.” [para. 253]

This passage rests on a mistaken premise. IHL authorizes States to attack two groups of persons in NIACs: civilians directly participating in hostilities and members of organized armed groups carrying out a continuous combat function. As regards the first group, CA3 and Article 13(3) of AP II stipulate that civilians lose their immunity from attack for such time as they are directly participating in hostilities. In contrast to the human rights standards on which Leggatt J seems to rely in this passage, during such time they may be lawfully killed even where they do not presents an ‘imminent threat’ to life. As regards the second group, it is important to realise that persons carrying out a continuous combat function cease to be civilians for as long as they remain members in the organized armed group by virtue of their continuous combat function. The capture of such a person does not, in itself, sever his lasting integration into the organized armed group to which he belongs. He does not become a civilian merely by virtue of his capture, but remains a fighter subject, in principle, to direct attack for as long as his membership in the organized armed group continues. Of course, during his detention, the authority to attack him is suspended, for persons who are hors de combat may not be made the subject of attack. The authority revives, however, as soon as he is no longer hors de combat, engages in hostile acts against his captors or attempts to escape. Consequently, the authority to kill persists for as long as membership in the organized armed group persists, although that authority is suspended following capture and during detention. Contrary to Leggatt J’s finding, the detaining State’s continued authority to kill a person carrying out a continuous combat function is therefore capable of serving as a legal basis for its authority to detain him.

Accordingly, the legal basis for status-based detention is both implicit in the scheme of CA3 and AP II, as a necessary corollary of the implicit authority to kill, and founded in customary international law. This conclusion is confirmed by the reality that detention is accepted and well-established in NIACs as a matter of State practice.