Introduction
Russia’s war of aggression has sparked intense public debates about whether and how to support Ukraine across many Western States over the past three years. These debates capture the heart of why I wrote this book and why I believe it needed to be written. From the early days of the war, Western States have emphasised that they would not take steps that would render them parties to the conflict under international law. Still, every proposed change in the nature of assistance has been discussed in terms of its effect on party status.
These debates have shown that there is a need for reflection on the concept of party status on two fronts. First, there has been confusion as to what it would mean, in legal terms, to become a party to the conflict. Some of the actual reasons for why we should pay attention to party status have been overlooked. Secondly, it remains unclear how to determine when an entity becomes a party—where that line is drawn and when it is crossed. This two-fold question is precisely what my book is about: why does party status matter and how is it determined under international law?
The question is chiefly relevant today because of the confusion and uncertainty in current debates about party status. The paradox is that, when I first started thinking about the topic, it was because the issue was receiving little attention at all. This was so although it seems to have proved a tricky issue in many major international and non-international armed conflicts. Identifying parties is tricky because armed conflicts are often fought in co-operation between multiple States, armed groups, or international organisations, with varying degrees of involvement. Increasingly diverse patterns of co-operation are characteristic of contemporary armed conflict—and they make it challenging to identify who among different co-operation partners qualifies as a party. Moreover, when multiple entities cooperate in armed conflict, responsibility for protecting individuals can be diffused among them—a problem that the law must confront.
My book aims to contribute to a clearer understanding of party status. It does so in a two-fold way. First, the book systematises the ways in which party status is relevant under international law. Secondly, the book puts forward a common analytical framework for identifying parties in all types of armed conflict, with a view to capturing the complex co-operation patterns that we see in today’s wars.
The legal relevance of the concept of party status
In political debates in Western States regarding Ukraine, party status has featured so prominently partly because of the significant political implications that it would have for Western States to be ‘at war’ with Russia. There seems to have been an underlying assumption that being a party alongside Ukraine would somehow entitle Russia to use force against Western States. That legal connotation of party status is reminiscent of the traditional meaning of being in a ‘state of war’. War was considered a separate legal sphere from peace, a sphere in which the contestants brought each other down by force. Such a conception of war may already distort nineteenth century international law (see here and here) and is certainly difficult to square with how international law regulates war today. Chiefly, the prohibition of the use of force applies between parties to an international armed conflict, and States also remain bound, for example, by human rights law. Being a party therefore no longer places the belligerents in an entirely separate legal sphere (although it does still have significant legal implications, as I will explain). Accordingly, Russia would, of course, commit further violations of the jus ad bellum if it were to attack Western States, even if these States were to be considered parties to the conflict. Conversely, contrary to what officials have sometimes stated or implied, becoming a party alongside Ukraine would not as such violate international law and the action making a State a party would be lawful under the jus ad bellum as long as they remain within the confines of collective self-defence. Legal clarity is important here, though it cannot replace an assessment of the political risks of using force.
So the partial blurring of the traditionally separate spheres of peace and war in international law is one wider development that calls us to re-examine what party status means today. A second such development is that international law in war increasingly centres on the individual as an addressee of rights, obligations, and responsibility. This ‘humanisation’ and ‘individualisation’ calls for re-considering the legal relevance of the collective entities between whom war is fought, that is, the parties. A third development is that war is increasingly regulated as a concern to the international community as a whole, rather than just a matter between two parties as ‘duelists’.
Against the background of these three wider shifts in the international legal order and international legal thought, the book shows that party status still is a crucial concept because the international legal regulation of armed conflict remains, in significant parts, organised around party status. At one level, parties bear central sets of obligations under IHL, both regarding the conduct of hostilities and regarding the protection of individuals, as well as certain permissions (though traditional ‘belligerent’ rights are more narrowly confined today, particularly by the jus ad bellum). In addition to the parties being addressees of international law themselves, the protection, rights, duties, and responsibility of individuals and third States in armed conflict are also determined by reference to the parties: it is in the relationship to these other addressees that party status has some of its central legal significance. For individuals, it is the nature of their connection to the parties that determines, for example, whether they qualify as combatants and commit war crimes (for example as part of the indicators used for assessing the nexus requirement). For third States, knowing who is a party matters not only under the traditional law of neutrality, but also, for example, regarding the duty under Common Article 1 not to provide assistance to IHL violations by the parties. Overall, an analysis of party status helps understanding how the broader shifts (noted above) in international law’s regulation of war actually play out and better grasp the structure of the regulation of armed conflict as a whole.
The legal framework for identifying co-parties
The book then develops an account of the legal framework for identifying parties to an armed conflict, whether international or non-international. I do so with a focus on those conflicts where it is particularly relevant and challenging to identify parties, because there are multiple potential parties on one or both sides of the conflict: I call these ‘co-parties’ in ‘multi-party conflicts’.
The first criterion for becoming a party requires that a State, IO, or armed group must carry out acts with a direct connection to hostilities. Speaking of the acts of a State, IO, or armed group presumes that the acts of individuals can be attributed to the potential co-party (which can be tricky, for example, in multinational forces). Regarding the quality of the acts, there is evidence in international practice that a potential co-party need not—on its own—perform acts that would suffice to create an armed conflict in the first place, as long the acts of all co-parties taken together suffice to do that. Still, hostilities are the essence of the conflict relationship between the parties. Structurally, therefore, the acts of an entity must form part of these hostilities for it to become a party. Hostilities can be defined as acts which cause harm to the adversary and so the acts of a (co-)party must have a direct connection to such harm. What exactly a ‘direct connection’ means is not settled. A practical way forward is to rely on how the ICRC understands ‘direct causation of harm’ in the context of civilian direct participation in hostilities, namely as causing harm in one causal step.
The second criterion concerns the character of the relationship between parties on the same side (i.e. co-parties). In order to become a co-party, the acts of an entity must be co-ordinated with the other party or parties on the same side. It is not enough to fight a common enemy: one State, IO, or armed group can be simultaneously involved in multiple, separate conflicts. What ties the acts of multiple entities together so that they become co-parties is the fact that they co-ordinate their military operations such that they build on one another as contributions to one armed conflict. The exact degree of co-ordination required is hard to pin down. It is helpful to keep in mind that IHL envisions (co-)parties as central players in armed conflict; and as such they have the primary responsibility that the conflict is conducted in accordance with IHL and thus decide how the conflict is conducted. Accordingly, it makes sense to require that the co-ordination must be such that each co-party has a role in the decision-making processes on the co-ordinated military operations.
If we have a direct connection to hostilities in sufficient co-ordination with fellow co-parties, then party status does not depend on whether the entity wants to be a party or not. Leaving declared wars aside (which remain possible but are rare), States, IOs, or armed groups do not need to intend or know the legal consequences of their acts regarding party status. However, they need to be aware that they are carrying out sufficiently co-ordinated acts with a direct connection to hostilities. I argue that this subjective dimension of knowledge is inherent in the notion of performing such acts: an entity cannot perform them without being aware of what it is doing.
To illustrate how the criteria may operate, consider the different types of military assistance provided to Ukraine. Supplying weapons or providing training— does not have a sufficiently direct connection to hostilities. It is only the actual use of the weapons or the trained skills that directly cause harm. In contrast, intelligence that has notably been provided by the US to localise or verify specific targets can be part of the targeting process, and thus of concrete military operations. Reports suggest that such intelligence was closely co-ordinated with the operational decision-making processes, and that the US was aware of the role of the intelligence. (For a more in-depth application of my account to the different forms of military co-operation in Russia’s war of aggression, see here.)
In terms of interpretive method, the book does not claim that these criteria are enshrined in a specific rule of customary international law, inductively borne out by sufficiently widespread and consistent practice accepted as law. Instead, I have discerned the legal framework from the structure of the system of legal regulation of armed conflict, by way of systemic interpretation. This systemic interpretation draws on the book’s earlier analyses of the legal position of parties. At the same time, the book shows how the criteria that I discern resonate with how party status has been understood in the practice of States and IOs in past and ongoing armed conflicts. In that sense, I have built my account deductively and confirmed it inductively. To make the findings of the book useful in practice, they have fed into a Chatham House research paper, which is based on discussions with legal advisers from a number of States and IOs.
In a final step, the book draws out key implications from the co-party framework, implications for how international law allocates obligations in armed conflict. Specifically, I show that the positive obligations of parties have particular implications for co-parties, regarding the acts of their fellow co-parties. These duties go beyond what third States would need to do under Common Article 1 to ensure that the parties do not commit IHL violations. What I try to show here is how the co-operative patterns that make entities co-parties can also be avenues for ensuring legal protection of individuals in armed conflict. (For a more detailed argument of mine on these duties’ legal bases and operation, see here.)
In sum, I hope that, through the lens of the concept of party status, my book contributes to a clearer understanding of how the structures of international law in this field can respond to the challenges of co-operation in armed conflict. I am grateful to the editors of the blog for hosting this symposium as well as to the commentators and I look forward to the discussion.
