The Involvement of Supporting States in International Armed Conflicts, A Practical Approach

[Jérôme de Hemptinne is an Assistant Professor at Utrecht University]

Several posts have been devoted to the delicate question of whether Western States could be implicated in an international armed conflict (IAC) against Russia because of the military, financial, and intelligence support they provide to Ukrainian authorities (see here, here, here, and here). The same question could also be raised regarding the assistance furnished by the United States and some European States to Israel: could this make these States ipso facto parties to an IAC between Israel and Palestine – assuming that this conflict is indeed considered an IAC, a position that is subject to controversy – due to their supplying activities? If so, under what conditions? As international humanitarian law (IHL) does not provide an answer to this question, the following theoretical approaches have been called upon to address it: neutrality, use of force, complicity, and the ICRC ‘support-based approach.’ However, none of these options offer convincing solutions. This is not surprising, as they were not originally conceptualized to determine the personal scope of application of IHL, and are thus difficult to transpose in this context. 

In this post, I suggest delving into a more pragmatic path rooted in the IHL normative consequences that flow from becoming a party to an existing IAC. But before exploring this avenue, let me briefly review the main pitfalls of the above theoretical approaches. 

Theoretical Approaches

The law of neutrality – which confers rights, for instance of inviolability, and imposes obligations, mainly of impartiality and abstention, on neutral States (see 1907 Hague Conventions V and XIII and customary international law) – has often been invoked to determine when assisting States are involved in a conflict. That said, neutral States do not necessarily become belligerents under IHL because they violated their obligations under the law of neutrality, as sometimes argued. IHL and the law of neutrality are two distinct bodies of international law subject to different regimes (see here, here, and here). Moreover, establishing a direct linkage between these regimes would render IHL applicable to all types of assistance – including allowing a belligerent to use its territory as a base of military operations or as a means of passage – that could potentially violate the law of neutrality. As I will show below, this would extend the scope of application of IHL well beyond what is reasonably acceptable and necessary. 

It has rightfully been argued that the law governing the use of force is not particularly helpful either (see here, here, and here). Indeed, as a matter of principle, IHL applies regardless of the origin and cause of the conflict. In any case, it remains unclear whether – and if so, when – the provision of assistance by a State to another State involved in an IAC amounts to using of force under ius ad bellum (even though, according to the Nicaragua (para. 195) and Congo (para. 164) Judgments, the ICJ seems to recognize that ‘arming and training’ an armed group combating State armed forces could be qualified as using force against these forces). 

A priori, the rules governing the responsibility of a State for complicity under Article 16 of the Articles on State Responsibility offer a more promising avenue – an avenue which has, in fact, been less explored by scholars (paras 216-221 and here). Admittedly, the purpose of these rules is not to determine the conditions under which States becomes a party to an IAC, but rather to establish the responsibility of a State that provides aid or assistance to another State and, in so doing, facilitates the commission of an internationally wrongful act by the latter. It could, nonetheless, be contended that the test used to identify the relationship between the assisting State and the assisted State for the purpose of classifying a conflict under IHL should be the same as the one employed for attributing an action carried out by the assisted State to the assisting State under the law of State responsibility. As we know, the question of attribution is essential for determining whether a State is involved in an IAC when it exercises control over the military operations conducted by an armed group. Indeed, as recently emphasized by the ICRC in the 2016 Commentary to Article 2 of GC I, (para. 268), “[…] by virtue of this operation, the actions of the armed group can be considered as actions of the intervening State and the relationship of subordination can be established.” That said, such a logic cannot easily be transposed in the context of establishing the responsibility of a State for complicity. As noted by the International Law Commission in its 2001 Commentaries (p. 67 para. 10), ‘[i]n accordance with article 16, the assisting State is responsible for his own act in deliberately assisting another State to breach an international obligation by which they are both bound.’ In other words, the assisting State is not responsible for the international wrongful act committed by the assisted State. There is thus no question of defining the proper attribution relationship between the assisting and assisted States that could be replicated in the context of determining the personal scope of application of an IAC. Furthermore, it is generally accepted that Article 16 covers a broad range of activities. For instance, it may include the simple provision of logistical or financial assistance (2001 Commentaries, p. 67, para. 9). Once again, if such test were to apply in the context of IHL, the circle of belligerents would be extended far beyond what is reasonable for the application of the rules governing the conduct of hostilities (‘Hague Laws’) or the protection of individuals and objects that belong to them (‘Geneva Laws’). 

Lastly, pursuant to the ‘support-based approach’, the ICRC has examined this issue from the perspective of a State or a multinational force providing support to another State engaged in a pre-existing non-international armed conflict (NIAC). According to the ICRC, for the contributing actor to become a party to that conflict, the following four conditions must be fulfilled: ‘1) there is a pre-existing NIAC taking place on the territory where the third power intervenes ; 2) actions related to the conduct of hostilities are undertaken by the intervening power in the context of that pre- existing conflict; 3) the military operations of the intervening power are carried out in support of one of the parties to the pre-existing NIAC; and 4) the action in question is undertaken pursuant to an official decision by the intervening power to support a party involved in the pre-existing conflict’ (see ICRC support-based approach, p. 1231). Even if these conditions could be analogously applied to an IAC context – we will revert to these requirements below – it must be acknowledged that the ICRC does not provide the foundational basis for these principles. They appear to be grounded in the same logic as the theory of ‘direct participation in hostilities’. However, the purpose of this theory is entirely different: determining under which conditions an individual – not a State – who participates in hostilities – not in a pre-existing IAC – loses protection from an attack – not ‘is involved in that IAC’. 

A Practical Approach 

In reality, none of these theoretical approaches offer persuasive answers to determine when a supporting State becomes involved in a pre-existing IAC. I wish to emphasize one point here: this is not a typical issue of material scope of IHL, where it is necessary to assess whether an IAC exists between belligerents. Rather it concerns delimiting the personal scope of IHL in a pre-existing IAC when a third power supports one of the belligerents already involved in this IAC. To tackle this matter, I suggest taking a different route: first examining the potential legal ramifications of a State joining an ongoing IAC before drawing conclusions on its conditions of participation to that conflict. Let us consider the Hague Laws and the Geneva Laws separately.

Regarding the Hague Laws, it should be highlighted that, at first glance, there is no need to apply the rules regulating the conduct of hostilities to supporting operations. Indeed, in an IAC, as soon as minimum hostilities occur between belligerents, the application of IHL is triggered (see 2016 Commentary to Article 2 of GC I, para. 236). A priori, when there are no direct confrontations between the contributing State and the opposing party, the laws governing the means and methods of warfare should not apply. However, a more nuanced approach is warranted upon closer examination of the matter. Bringing a supporting State into the IHL equation could well be relevant if the assistance provided is closely related to specific combat operations between the two States involved in the pre-existing IAC. In these circumstances, the supporting State’s adherence to the principles governing the means and methods of warfare – such as the principles of precaution in attack, distinction, and proportionality – is indeed essential to prevent (or minimize) collateral damage (pp. 33-35). In other words, these principles should govern not only actual confrontations between the supported State and its adversary – as traditionally envisaged –, but also the assistance given by the supporting States when such assistance has a concrete impact on the conduct of specific hostilities. This usually requires that the supporting and supported States maintain close relationships in the conduct of military operations, for instance, by integrating their respective command and operational structures (pp. 33-35). To take an example, if intelligence is provided regarding the location of a particular military objective and nearby civilians, it is crucial that the provider take all necessary precautionary and verification measures to ensure that civilians are spared when this objective is attacked based on the intelligence furnished. This also holds true if specific weapons are supplied to strike a particular military target. The supplier of these weapons must make sure that they are the most suitable to minimize collateral damage. On the other hand, States cannot be expected to uphold Hague Laws when offering general financial, logistical or military types of support that are unrelated to specific combat operations. 

Turning now to the Geneva Laws, their application to the relationship between the supporting State and the adversary of the supported State could also become essential for ensuring the protection of all civilians belonging to these parties when they are in the hands of the opposing belligerent. For instance, in the Ukrainian conflict, this includes Western nationals who are located in Russia or detained by Russian authorities, and vice-versa, Russian nationals located in Western countries or detained by Western authorities. If IHL applies to the supporting operations, these persons will ipso facto benefit from all guarantees offered to ‘civilian populations’ by Arts 13 to 26 of Geneva Convention IV (GC IV). In addition, if the State of nationality of these civilians no longer has normal diplomatic representation in the State in whose hands they are (Art. 4 of GC IV), they could avail themselves of the protections entrusted to ‘aliens in the territory of a party to the conflict’ by Arts 35 to 46 of GC IV, in particular the right to leave the territory (Arts 35, 36 of GC IV), or the right to be treated with dignity if they decide to remain on that territory (Arts 37–46 of GC IV). Furthermore, it could be argued that the level of direct involvement of the supporting State in hostilities, along with the proximity of the relationship between the supporting and supported States, often corresponds to a higher probability of civilians encountering persecution or mistreatment upon detention (especially if diplomatic relationships between the two concerned States are broken).  

It should be noted in passing that this protection is, in principle, not needed for the members of armed forces of the supporting State or of the adversary that are arrested and detained by the other belligerent, since these individuals will, in principle, automatically benefit from the safeguards of the GC III as soon as they fall in the power of enemy. Indeed, the arrest of prisoners of war will by itself trigger the application of the laws governing IACs. As noted by the ICRC, ‘[…] under the Third Convention, if members of the armed forces of a State in dispute with another fall into enemy hands, they are eligible for prisoner-of-war status regardless of whether there is full-fledged fighting between the two States’ (para. 239). 

Furthermore, as aptly demonstrated by an excellent report of Chatham House (pp. 35-36) on the matter, becoming a ‘co-party’ to an IAC entails other significative legal effects. Due to space constraints, I cannot examine all of these effects here. I would just like to point out the necessity for a supporting State to take all ‘possible’ measures to search for, collect and care for missing, wounded, sick and dead individual (Arts 15 GC I, 16 GC IV, 33 AP I). Similar to the legal implications mentioned above, it could not be required from the supporting State to respect these obligations – albeit they are obligations of means – if that State is not concretely involved in hostilities and closely related to the supported State through direct operations of support.     

Concluding Thoughts 

In a nutshell, the normative analysis of both the Hague and the Geneva Laws suggests that the following factors should be taken into account when determining whether the personal scope of a IHL could be extended to a third State providing support to another State: (i) the pre-existence of an IAC between the supported State and another belligerent; (ii) the direct nature of the support provided to specific military operations conducted by the supported State; (iii) the closeness of the operational relationship between the supporting State and the supported State in carrying out these military operations; and (iv) to a certain extent, the risk that this relationship may pose to the well-being of civilians of the supporting State and its adversary, especially when diplomatic relationship between the two States no longer exists.