In recent weeks there have been two significant and related debates on Just Security about the justification for the use of force against non-state armed groups and the place of human rights in non-international armed conflict (NIAC). Both debates address aspects of a larger question that has remained unresolved throughout the years since 9/11: how should we understand the legal framework that defines and limits a state’s resort to military force  against an armed group that threatens its security or territorial integrity? In the following analysis, I propose a further refinement to the discussion, drawing on a forthcoming article that will appear in International Law Studies concerning the justification for the resort to force against members of non-state armed groups.

The bottom line: human rights law provides the set of rules for when a state may resort to military force against members of a non-state armed group, but that is not the end of the analysis for human rights law. Because human rights law performs this function on an individual basis, it continues to circumscribe a state’s military operations during the subsequent hostilities.

In the last fifteen years, there has been an extraordinary amount of discussion about the United States’ right to use military force against fighters linked to al-Qaeda or “associated forces.” But to a remarkable degree, the arguments on both sides of this question have tried to define the powers that the United States possesses by reference to whether an armed conflict exists, how far it extends, and what powers international humanitarian law (IHL) confers in such a conflict. As Eliav Lieblich has noted in his important article and Just Security post, such an approach neglects the fundamental question of whether the resort to force itself is justified.

In international armed conflict, we are used to the idea that jus ad bellum determines the legality of the use of force between states. IHL regulates the conduct of hostilities, but it cannot be said to give positive authorization for any incident of force, because it does not consider whether the action falls within the scope of force that is justified under jus ad bellum. By neglecting the question of the justification that is needed for the use of force against a non-state group – and how far it extends – the debate over the US campaign against al-Qaeda and “associated forces” has been normatively and analytically impoverished, since it has failed to link the legality of the use of force to what is necessary and proportionate for a legitimate purpose.

Clearly, though, the jus ad bellum regime based around the UN Charter cannot regulate the resort to force against a non-state group, because it applies only to the use of force between states; it is silent as to action taken against internal insurgents, or conducted against an external armed group with the consent of the host state. Instead, as Lieblich and Jan Hessbruegge observe, we must look to human rights law to play this role.

If we imagine a state confronting an organized group in a pre-armed conflict context, it is clear that the only international law constraint on the state’s use of lethal targeting or detention without trial – the classic measures associated with the resort to armed force – is found in human rights law. Human rights law does not absolutely prohibit such measures (for example it might permit them in the face of an imminent threat to life or during a state of emergency) but it confines them within the tight bounds of what is strictly necessary and proportionate to protect life or restore public order. In this way, human rights law has a justificatory structure that closely parallels the operation of jus ad bellum in an inter-state context. A state that launched a full-scale military campaign against a non-state armed group without adequate justification would violate the human rights of at least some of those targeted or detained, as well as others killed as an incidental effect of the campaign.

However, Lieblich’s suggestion that human rights governs the first resort to hostilities between a state and a non-state group seems to fall short of providing a complete account of how the justification for the use of force functions in such circumstances. After all, as the discussion launched by Adil Haque has emphasized, the accepted view is that international law situates the threshold of NIAC not at the first resort to armed force, but at the moment that hostilities reach a certain level of intensity. States do not “launch” NIACs; instead these come into existence as a factual matter due to the accumulation of acts of force conducted by both parties. The key analytic and normative question, then, is how the justification for the resort to force attaches to that moment of transition, and what that implies for the use of force in the subsequent armed conflict.

In international armed conflict, hostilities take place between two sovereign and collective entities; to the degree that the resort to force is justified, it can be employed against any member of the opposing state except insofar as he or she is protected under IHL (i.e. civilians and combatants who are hors de combat). But human rights law governs the use of force against individuals. Up to the threshold of NIAC, at least, it requires that each specific act of targeting and detention be justified in itself in terms of the impact that it has on the life and liberty of those individuals affected by it.  And, in my view, it is impossible to see anything in the transition to NIAC that would change or displace that essential logic.

As I suggested above – and as others including Derek Jinks and Adil Haque have eloquently argued – IHL may be applicable once an armed conflict is underway, but it cannot be said on its own to provide positive authorization for any act of force; instead, it regulates the conduct of hostilities by prohibiting certain actions by each party on an equal basis. When a state uses force in violation of the jus ad bellum, its actions remain illegal even when they comply with IHL. Similarly, an insurgent group in a NIAC does not acquire the right to carry out military actions, even where they would be permitted under IHL, because it is presumptively forbidden from doing so under domestic law (which functions as a kind of jus ad bellum for a state’s citizens). To the degree that IHL privileges or immunizes certain forms of conduct in international armed conflict, as Charles Kels rightly pointed out in a recent response to Haque, this should be understood as providing protection against criminal prosecution for the individual involved, rather than positive authority under international law for the state responsible.

Nor is there anything in the transition to NIAC that would somehow elevate the state’s justification for the resort to force from an individual to a collective level. No qualified prohibition on using force against an armed group per se exists in international law, such that the transition to NIAC could lift it. Indeed states have been adamant that the extension of IHL to non-international conflict should not be seen as indicating in any way that an armed group involved in armed conflict thereby acquires a collective legal status that might put it on a par with the state. By reserving to themselves the right to treat insurgents as individual criminals or traitors under domestic law, states at the same time deprived themselves of any claim to treat the armed group involved as a collective entity for the purpose of the state’s prosecution of the conflict.

If this argument is correct, it means that we must understand human rights law as adjudicating the justification for the state’s resort to force against individuals within its jurisdiction both below and above the NIAC threshold. The transition to armed conflict brings into play a set of protections and prohibitions for both parties, but it does not change the individual basis on which the state’s authorization for the resort to force is calculated. This does not of course mean that human rights law will assess the right to life and liberty identically in normal peacetime conditions and during armed conflict. It is implicit in the justificatory structure of human rights law, assessing the state’s actions against their necessity and proportionality with respect to a legitimate purpose, that its application is shaped by the prevailing context. The closer that the conditions resemble active and intense hostilities, the more the interpretation of human rights standards will map onto the rules of IHL, as the case law of the European Court of Human Rights indicates.

Nevertheless, if we understand human rights law and IHL as fulfilling distinct and separate functions with respect to acts of force in NIAC – as providing a justificatory and regulatory regime respectively – it may help to clarify the relationship between them. Since the two bodies of law do not apply in parallel in this respect, at least in NIAC, there is no need to look for a lex specialis rule to reconcile their differing requirements. There is no contradiction involved in the idea that the targeting or detention of any fighter for an opposing armed group is permitted under the regulatory regime of IHL, but that in some cases it may not be authorized under the justificatory regime of human rights law. In this sense, human rights law remains antecedent to IHL in determining how far the resort to force against individuals within the state’s jurisdiction is justified. A significant consequence of this approach is that there can be no automatic entitlement to status-based targeting or detention in NIAC, because the justification for the resort to force never reaches to the collective level that could alone provide a foundation for it.

In this short space, I have provided only a brief and preliminary sketch of the implications of understanding human rights law as justifying the resort to force against members of non-state armed groups. In particular, the rise of extraterritorial campaigns against such groups raises a number of difficult questions about how the traditional understanding of the requirements of human rights law might apply in that new context. Those are subjects for another discussion. A key point, however, is that states cannot simply claim a legal right to target or detain any member of an opposing armed group during NIAC; instead their actions constitute a claim about what is necessary and proportionate under the circumstances, and establish a precedent that other states may later invoke.