Alex Wentker’s book, which will stand as the definitive work on co-party status for years, offers an extremely careful and comprehensive look at the nature and implications of being a co-party to an armed conflict. In addition to providing a range of insights about how to assess co-party status, his book prompted three reflections. One is a modest question about his approach to “collective contributions” of states to a conflict; the other two involve issues on which I think that he may have undersold the importance of his conclusions.
1. Collective contributions to an armed conflict. In his opening post, Wentker summarizes his argument that states should and do assess their collective contributions to acts against an enemy, rather than requiring each actor to assess its own contributions against that enemy, when determining that an armed conflict exists. As he writes in his opening post:
“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.”
Wentker admits that it is difficult to imagine scenarios in which any one state’s contribution alone would not create an international armed conflict, but where the contribution of multiple states would. The one example he gives is a blockade (115), an act that is relatively uncommon today. In contrast, he explains that it is easier to imagine a scenario involving non-state armed groups where individual state contributions might fall short of creating a non-international armed conflict (NIAC) but where collective state contributions would produce sufficiently intense fighting to cross the NIAC threshold.
In either case, to require individualized assessments often will be unduly formalistic and, as Wentker notes, might create real evidentiary difficulties. All this is to say that I agree with his conclusion that we should assess collective contributions when making determinations about whether an armed conflict exists – and indeed the practice that he cites from various international tribunals supports that view.
Where I part ways is with his assessment of the NIAC-based state practice leading to this conclusion (117-20), which I find more ambiguous than he does. Wentker offers several examples of state practice in which a state purported to apply IHL to an operation without assessing whether that state’s individual acts (and the non-state actors’ response) rose to the NIAC threshold. For example, Wentker notes that the United States stated that IHL applied to coalition operations against ISIS, without assessing each contributing state’s contributions against the NIAC’s intensity threshold. He cites Canada as asserting that IHL applied “to its first airstrikes conducted in Syria under Operation Impact in 2015,” as well as statements by the Dutch and Belgian militaries, which acknowledged that IHL applied even to their first strikes against ISIS targets (118) – at a point at which those states (individually) had not yet entered a NIAC with ISIS.
But the statements from these states are not surprising and do not, I think, tell us much about whether the states internally made collective or individual assessments about the level of fighting against ISIS and their role in that fighting. The reason for that is that some states now seem to accept that IHL does (and should) apply to one-off military strikes against groups taken in individual or collective self-defense, whether or not those strikes lead to a NIAC. As David Kretzmer wrote in 2013, “All actions of a state that exercises its right to use force in self-defence must comply with jus in bello.” Although some may disagree with the idea that IHL applies to a “first strike” against a non-state armed group (because an armed conflict is not yet underway, meaning that under a traditional approach IHL would not yet be applicable as the governing body of law), why should the international legal rules governing a first strike be different from those governing the second, third, and fourth strikes, at least when there is a clear sense that the first strike will be only one in a series of military operations? As a result, the decisions by the United States, Canada, the Netherlands, and Belgium to apply IHL rules such as distinction and proportionality to their first strikes against ISIS are not surprising. At the same time, those decisions do not provide much information about whether those states have adopted a “collective assessment” approach to co-party status.
2. Domestic implications. Wentker deliberately focuses on the international aspects of being a co-party, and he understandably de-emphasizes the domestic legal implications of co-party status (7-8). Nevertheless, the domestic implications of being deemed a co-party – including for parliaments as they execute their legislative and oversight roles – are very important and offer additional fodder for the idea that his book fills an important gap.
Let’s assume that few parliamentarians understand the nuances of what it takes for a state to become a co-party and what the international law implications are for doing so. This means that when they appropriate money for their state’s military to train and equip the military of another state that is in an armed conflict; enhance their intelligence services’ authorities to share certain information with foreign governments; or authorize their special forces to undertake certain coalition counter-terrorism operations, they are making those decisions without a clear understanding of whether any of those authorities implicate the party status of their own state. They likely also lack knowledge about the implications of that status, meaning that they may – on the one hand – join the chorus of actors who believe that becoming a co-party to a conflict allows the aggressor in that conflict to lawfully attack the new co-party, or – on the other hand – claim that the aggressor has committed war crimes against its forces by virtue of striking them, even if the aggressor targets those forces in ways that do not otherwise violate IHL. In short, developing a common understanding of co-party status would benefit not just a state’s leadership, military, and intelligence services but also the democratically elected legislators in those states. With a clearer understanding, those legislators can draw clearer, better-informed lines when legislating or appropriating for armed conflicts and can bring to bear sharper oversight of military activity during those conflicts.
3. Shaping co-party behavior. Perhaps the most important consequence that flows from becoming a co-party to a conflict is the obligation under IHL to take steps to enforce the other co-parties’ compliance with IHL. Wentker details these specific obligations (214-18), including the precautionary requirement to take “steps to ensure that civilians are spared by the military operations as a whole, including the contributions made by one’s fellow co-parties” (215). This might mean that a state would assist its co-parties in building precautions into target selection and verification (216). It may include a duty to “investigate potential IHL violations of other co-parties” (217).
There seems to be a very unfortunate trend in armed conflict away from compliance with IHL. The President of the ICRC recently stated, “We are witnessing a global and collective failure to protect civilians in armed conflict.” But perhaps if democratic coalition states take seriously their obligations to each other as co-parties to an armed conflict, we might see some improvement in the direction of a higher common denominator for IHL compliance within the coalition, rather than a drift to the lowest denominator. A state that is a co-party to a conflict should condition its participation in the coalition on the other members’ compliance with the precautionary measures that Wentker identifies.
I have previously argued that one state’s military and intelligence services can impose “peer constraints” on foreign services with which they cooperate, which can result in an increased commitment to the rule of law. I wrote:
One [intelligence community or “IC”] can impose forms of discipline or structural limits on the activities of its counterparts, particularly when it implements its own domestic and international legal obligations. Through various mechanisms—both formal and informal, public and private—one state’s IC can affect the way in which another IC conducts activities such as interrogation, detention, targeted killings, and surveillance; the amount and type of intelligence the other IC receives; and, less tangibly, the way in which the other IC views its own legal obligations.” They do so by offering the carrot of cooperation and the stick of refusing such cooperation, including the use of airspace, territory, or intelligence.
Wentker’s description of co-party obligations, if taken seriously by the co-parties, envisions a similar possibility. One co-party can drive the others toward a careful and serious approach to IHL, motivated not by the first party’s domestic legal constraints but by a shared set of international legal obligations. This may be the most important outcome of all for co-party status.
