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

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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.

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Ezequiel says

February 11, 2015

Thank you both for this interesting post. As I explain here http://papers.ssrn.com/sol3/papers.cfm?abstract_id=2559908, this could certainly be one of the arguments for detention in NIACs (but not the only one), especially having in mind two elements. Firstly, that States have the obligation to protect their own armed forces, therefore they would always prefer their soldiers to be detained rather than to be killed; and secondly, because the aim of detentions is to gain a military advantage. It's just a matter of IHL logic that parties to an armed conflict would hinder persons from continuing to bear arms.

Yet, I do not understand why you just take into account State practice, don't you think that armed opposition groups' detentions come in the same line?

Jordan says

February 11, 2015

Common Article 3, for example, does not expressly permit detention or expressly deny detention. In fact, it expressly contemplates "detention." In this circ. an implied authority to detain is possible if there is general practice and general opinio juris to support detention.
p.s. a new draft article "Human Rights on the Battlefield" is up on SSRN -- http://ssrn.com/abstract=2563329
Most of the attention is on human rights during an IAC, but some re: an internal armed conflict.

Ed Robinson says

February 11, 2015

Thanks for the interesting post. I think the extent of lethal force and detention international human rights law should allow in a NIAC is difficult – but I'm not sure it can be answered by finding an authorisation on the IHL side in order to manufacture a conflict of norms between it and IHRL, which IHL can then win along analogous lines to the Hassan outcome, as the UK government is seeking to argue.

In particular I struggle to follow the argument that IHL provides a right to one party to the NIAC to use lethal force against those participating in hostilities (and by implication detain them) but not the other. I agree the status of the parties to hostilities is unequal, but this is not because IHL imposes rules which discriminate between the state and the NSA, it's because of all the areas it doesn't regulate at all – e.g. the grounds on which hostile acts are protected from domestic prosecution. In the absence of inter-state conflict these are left to the state to regulate on its own terms subject to IHRL, and unsurprisingly domestic law will allow the state to use force and detain in ways not permitted to the NSA. State practice in NIACs is evidence of this, not of an international law authorisation.

Just regarding the reference to Korbely – as I read it the ECHR was looking there at common Article 3 in the context of deciding whether breaching it could have constituted a crime against humanity under international law as it stood in 1956. Their holding was thus only evidence of their view that killing the armed insurgent leader in a NIAC was not an international law crime, not that international law permits it to the extent of overriding conflicting IHRL rules.

Aurel Sari says

February 11, 2015

Jordan, thanks for the link!

Ezequiel, we do not discuss the practice of organized armed groups because, in contrast to States, IHL most certainly does not confer an authority on such groups to detain individuals in a NIAC. States and organized armed groups do not enjoy the same legal status or legal authorities under IHL.

Aurel Sari says

February 12, 2015

Ed, I don't think there is contradiction between our argument and your position. Yes, NSA's do not benefit from an authority to conduct status-based operations because IHL does not confer such an authority upon them. Yes, States may regulate the use of lethal force in their domestic law. What we are saying is that, in addition, there is also an authority under IHL to target and detain. Nor do I see a contradiction between your reading of Korbely and ours. Yes, the Court was concerned with establishing whether or not the killing of Kaszas was a crime against humanity. The reason why it did not qualify as a crime was because the Court found that (a) Kaszas was DPH-ing and (b) he could be targeted whilst doing so, in line with CA3. The Court's finding that Kaszas was a combatant and as such subject to lethal targeting is a necessary step in its reasoning. Our point is that it demonstrates and recognizes the duality of IHL: protection for some, targeting for others.

The argument I struggle with is the idea that domestic law is a sufficient basis for status-based operations. It is not. Art 2 ECHR does not allow status-based targeting either in IAC or NIAC and no Contracting Party can invoke its domestic law to justify a departure from this prohibition. Domestic law simply is not a sufficient legal basis for what Contracting Parties actually do in armed conflict or what they train their forces to do in such circumstances.

federico says

February 12, 2015

Your position is fully based on the complete and acritical endorsement of the theory of continuous combat function.

Ed Robinson says

February 12, 2015

Thanks for the response Aurel - I agree state practice in armed conflict doesn't fit within Art 2(2) of the ECHR. I don't think it necessarily follows that there must be an IHL rule which answers the problem. The Korbely case shows a distinction does exist between potential targets in a NIAC - but I see this as the distinction between conduct IHL prohibits (and in that cases, criminalises) and conduct on which it is silent and leaves to state domestic regulation. I agree such regulation doesn't preclude a co-existing IHL rule but think it does make it hard to argue that the occurrence of detention by states in NIACs must be evidence of a permissive rule of the sort that exists in an IAC.

Michael says

February 12, 2015

Very reasonable and eloquent line of argumentation - and convincing. Thank you.

Kevin Jon Heller says

February 12, 2015


Exactly right. No one is arguing that IHRL governs everything in NIAC; regardless of how we understand lex specialis, it's clear that the prohibitive rules governing targeting in NIAC come from conventional and customary IHL. But detention is different, because IHL does not regulate detention in NIAC beyond the minimal treatment standards in CA3 and APII. The applicable rules thus come from IHRL.

Auriel, you claim that your conclusion "is confirmed by the reality that detention is accepted and well-established in NIACs as a matter of State practice" -- yet you cite nothing in defense of that claim, and Dapo and Lawrence cite contrary practice that you do not address. Could you please provide evidence that states other than the UK claim that IHL, not their domestic law, provides authorization to detain in NIAC? The fact that they detain in NIAC is obviously not enough.

Aurel Sari says

February 13, 2015


I don't get how you can say that, regardless of what we think of lex specialis, IHLR does not govern everything in NIAC, given that the prohibitive rules on lethal targeting stem from customary and conventional IHL. If you leave aside lex specialis and impose on a State certain prohibitions on targeting under IHL and also a set of more restrictive prohibitions as a matter of IHRL, it is difficult to see how the more restrictive prohibitions of IHRL would not be the prevailing set of norms. One way around this is relying on lex specialis to the effect that the narrower IHRL norms do not previal where IHL applies. Another way is to recognize that IHL is not just prohibitive body of law, but also offers authorizations. In case of a conflict between such an IHL authorization and a contrary IHRL prohibition, the former prevails. You may think of this second approach more along the lines of systemic interpretation or 'accommodation' (as per Hassan) rather than as lex specialis.

As for evidence, see http://mfa.gov.af/en/news/7671.


Kevin Jon Heller says

February 13, 2015

Thanks for the citation -- but it supports my position, not yours. According to Section 2(5), "Afghanistan affirms that it has established an administrative detention regime under its domestic law which is... consistent with international humanitarian law, including the Additional Protocol II of 1977 to the Geneva Convention of 1949, and all of Afghanistan’s international obligations." So Afghanistan is quite clearly relying on domestic law to authorize its detention practices, not on IHL.

Aurel Sari says

February 13, 2015

Kevin, you're earlier point about 'the fact that they detain in NIAC is obviously not enough' cuts the other way too: 'the fact that they regulate detention in domestic law is obviously not enough to deny the existnece of an underlying authority in IHL'. I'm afraid that we read that provision differently.

Kevin Jon Heller says

February 13, 2015

In your post, you argued that your conclusion -- that IHL authorizes detention in NIAC -- "is confirmed by the reality that detention is accepted and well-established in NIACs as a matter of State practice." I pointed out, in response, that the mere fact that states detain in NIAC does not support your conclusion, because such detention could -- and often does, as Dapo and Lawrence point out in their post, citing specific examples -- reflect the fact that states look to their domestic law for authorization to detain. You now seem to be arguing that you do not actually have to identify any practice that supports your conclusion, because state detention in NIAC could be consistent with it. That seems fundamentally at odds with your post. If you want to claim that state practice is irrelevant to whether IHL authorizes detention in NIAC, fine -- make that claim. But if you argue that your position is supported by state practice, you need to do more than point out state practice is not necessarily inconsistent with your position.

As for the Afghan MOU, I will leave it to readers to judge whether Art. 2(5) views domestic law or IHL as authorizing detention. I will simply point out that reading "consistent with" as really meaning "authorized by" -- which I assume is your argument, though you don't spell it out ("I'm afraid that we read that provision differently") -- renders a number of other Articles in the MOU that use "consistent with" incoherent, such as Art. 14's provision that "All cooperation under this MoU is to be consistent with the Participants’ respective rights, obligations, and commitments under international law."

Aurel Sari says

February 13, 2015

Kevin, thanks for probing these points! Just to clarify our argument. The main point we make is that the authority to detain is not excluded by the language or nature of CA3 and AP II as Leggatt J held, but inherent in the very scheme of IHL applicable in NIAC. We see this confirmed by the language of the relevant norms. We also see it confirmed by State practice, although I take the point that unambiguous examples of State practice on detention (as opposed to targeting) are not legion. However, this does not undermine our main argument, since what we said is that State practice ‘confirms’ our reading, not that it carries that reading all on its own. I therefore do not see the fundamental inconsistency that you mention.
Regarding the Afghan MoU, a narrow textual reading of its individual terms does not support either your position or our position. The MoU refers to domestic law and IHL, without spelling out their relationship in express terms. Just because the text mentions domestic law, it does not follow that this is the legal basis for detention. In the same way, just because it mentions IHL, it does not follow that it recognizes IHL as the legal basis for detention either.
Rather, it is reading the text as a whole which I believe supports the argument that IHL is the legal basis for detention. The MoU draws a clear distinction between law enforcement detention and administrative or security detention. Section 2 defines detention facilities as ‘as facilities established to hold persons consistent with international humanitarian law, including Additional Protocol II of 1977 to the Geneva Convention of 1949.’ The entire rationale for holding persons outside of the law enforcement process is therefore defined with reference to IHL. To my mind, this confirms that IHL provides an underlying legal authority to detain such persons. The fact that administrative or security detention is further regulated by domestic law does not contradict this. Nor is it excluded by a narrow textual reading of the terms of the MoU. Notice how Section 5(a) and (b) contrast ‘consistent with’ and ‘in compliance with’. I read ‘in compliance with’ to refer to the prohibitive aspects of detention under IHL, while ‘consistent with’ refers to its permissive (authorizing) aspects. Otherwise, subsection (b) would add nothing to what has already been said by subsection (a).

Liron A. Libman says

February 16, 2015

Thanks, Auriel, for an interesting post.
I certainly agree with your general depiction of IHL as balancing military necessity and humanitarian considerations. Ignoring one of these interests in the interpretation of IHL will produce eschewed outcomes.
More specifically, I wish to comment on the debate about the significance of domestic law to the question whether state practice indicate to the existence of a customary IHL rule that authorize detention in NIAC. I think it is irrelevant.
The reason is that domestic legislation may assume such a rule and aim to implement it. This is reasonable considering the vagueness of customary rules and the practical need for concreteness in issues of detention. However, domestic legislation may as well imply that legislation was necessary due to the absent of a rule of IHL authorizing the detention.
The fact that the legislation or any other relevant document declares that it is "consistent with international humanitarian law" does not help. It can indicate either that the detention is authorizes by IHL or that the detention is not prohibited by IHL. If I understood correctly, there isn’t a dispute over the second proposition, just over the first one.
Another relevant example is the Israeli Incarceration of Unlawful Combatants Law, 5762-2002 (see an unofficial translation here: https://www.icrc.org/applic/ihl/ihl-nat.nsf/0/7A09C457F76A452BC12575C30049A7BD). The law apply to any fighter detained that is not entitled to POW status, whether the detention was made during IAC or NIAC. It declares, too, that "This Law is intended to regulate the incarceration of unlawful combatants not entitled to prisoner-of-war status, in a manner conforming with the obligations of the State of Israel under the provisions of international humanitarian law"(article 1). I don’t think one can learn from it anything else than an assumption that such a detention is not prohibited by IHL.

Claire says

February 18, 2015

frederico already said that your theory is based on an endorsement of the continuous combat function. Does your theory also apply to persons who are captured when DPH-ing, without actually having reached a level of continuous participation? If IHL authorises detention, it seems it would, but your justification for detention would not apply.