The legal issues surrounding military operations against non-State armed groups abroad are continuing to generate policy and legal debates. In an article just published in International Law Studies, I examined several questions arising, looking at the ius ad bellum (when a State may lawfully resort to military force), ius in bello (the rules that apply once hostilities exist), and the interplay with human rights. Here, I’d like to present a few key points emerging from the article in relation to some of the topics covered and provide a few examples of how a more accurate understanding of international law may inform policy choices in this space (including for example how and where governments fight the Islamic State).

Briefly, in relation to the ius ad bellum, I reached several conclusions in my research. First, that there is growing support that is becoming difficult to refute, allowing States to invoke self-defence in relation to armed attacks by non-state actors operating from the territory of other States and whose actions cannot be attributed to the territorial State. Second, that the debate over the so-called “unwilling or unable” test is a red herring, serving as a proxy for the real debate in the previous point. Simply put, if one accepts that self-defence can be invoked in relation to armed attacks by non-state actors without the territorial State being responsible, then “unwilling or unable” should be understood as nothing other than part of the existing necessity test. In short, it is not a new standalone test, and cannot be used to justify force in the absence of an armed attack and the principles of necessity and proportionality.  The flip side is also true: if one denies the use of “unwilling or unable” as part of the necessity test, then to all effects and purposes that is the same as denying the right to self-defence against independent non-state actors. The latter is, of course, a valid position, but in that case, let’s focus the discussion on the initial underlying issue rather than wage it by proxy. The third point of the ius ad bellum analysis, is that even if State A (the U.S.) has already invoked self-defence in relation to Group X (Islamic State) in State B (Syria), if State A wishes to violate the territorial sovereignty of State C (Libya; the Philippines) due to Group X’s activity from the latter, it must make a new case under the ius ad bellum, demonstrating the necessity to use force to avert armed attacks, for any new border it wishes to cross without consent.

Turning to the ius in bello, the article examined issues of classification and of scope. With regard to classification, one of the topics that has generated debate on this site (here, here, here) is the question whether force by State A against Group X on the territory of State B (without the latter’s consent) must necessarily lead to an international armed conflict between the two States. The question highlighted is not whether it could lead to an international armed conflict, as most everyone would agree that in some circumstances it might; but rather whether such force without consent must automatically generate an armed conflict situation between the two states, as seems to be implied by the latest ICRC commentary to the Geneva Conventions. My analysis was that any such automatic assumptions would be extremely problematic. While we tend to think of the higher end of the spectrum of force (e.g., a sustained air campaign), it is helpful to consider the issue also from the lower end of the scale. For example, the Rainbow Warrior incident was an operation using force without consent against a non-state actor in the territory of another state. French agents sank the Greenpeace-owned trawler (the Rainbow Warrior) in a New Zealand harbour. If one were to take the automatic approach to triggering IAC, then we would have to say that this incident created an armed conflict between France and New Zealand – and I daresay this is not a conclusion that many readers of this site would endorse. This issue is examined in more detail in the article, and the suggestion I offer is that in such circumstances a range of factors must be considered – including the nature of the force used, the effects of the force, and the combination of the objective and subjective aspects of belligerent intent. It also highlights the importance of recognising that violations of Article 2(4) of the UN Charter do not necessarily correspond with ius in bello classification, and each requires a separate analysis. Consent will often be determinative for resolving ius ad bellum issues, but for IHL classification purposes, rather than being determinative its relevance should be evaluated in combination with a range of factors.

On the matter of scope, the article addressed two issues, that of geographical scope (in which the case is made that IHL does not itself create geographical boundaries to the armed conflict), and the matter of “associated forces” and “co-belligerents.” The latter is an issue that has received excellent treatment elsewhere, especially with regard to how these terms came about being used by the U.S. In the article, I note that co-belligerency has been lifted from the world of inter-state armed conflicts and applied out of context in the sphere of non-State armed groups. An example of the problem this creates is that among States it may be possible to enter a conflict by declaration, while this is absolutely not the case for armed groups in non-international armed conflict (NIAC). Indeed, the US appears to have recognised that words are not enough. However, if the test is action, then we must further develop our understanding of the actions that would lead to a new group being considered party to a pre-existing armed conflict. Being under a single command and control structure, or a situation in which one organised armed group has control over another would be the obvious places to start. Beyond these lies a scale of activities with no obvious place to pinpoint the answer. Direct engagement in battlefield hostilities would be at one end of the scale, and coordination of lethal activities (such as dividing up zones of conflict and coordinating attacks) would likely also satisfy the test, but caution is urged with sliding toward a definition that encompasses amorphous notions of “support.” While a support-based approach can make sense in the context of States, just like the notion of co-belligerents, it does not translate easily into the sphere of NIAC, primarily due to the fluid nature of non-state actors and the difficulties in separating between civilians and members of armed groups. That being said, even if a determination cannot be made that a particular group has become party to the conflict, it is possible that individuals from that group might be taking direct part in hostilities on behalf of another group and lose individual protection even if their own group is not a party to the conflict. It would be legally unprecedented and unsound to refer to such individuals as “associated,” which some members of the U.S. Congress have proposed as part of authorizing force against the Islamic State. The proper test is the established targeting rule of direct participation in hostilities and relevant rules on detention, both of which might even sweep in the same individuals but under a proper legal framework. Grounding military actions in an established legal framework also facilitates interoperability among coalition forces.

Lastly, on the interplay with human rights law, the position taken is that there is no escaping the conclusion both that international human rights law applies extraterritorially, and that it applies during armed conflict. The open question is how to operationalise the interplay. Answering this question requires an approach that is capable of distinguishing between different types of circumstances and applying the two bodies of law concurrently in a manner that is practicable and gives appropriate weight to their object and purpose (for a recent publication on this topic see here). With regard to some of the military operations that take place extraterritorially against armed groups, I suggest that the proximity to active hostilities and control over the area (including through a third party such as a cooperative host State) are key factors in this regard. The interplay with human rights law, together with the ius ad bellum, serve to limit unwarranted use of military operations. If State B, for example, is capable and ready to detain the individuals that State A claims are engaging in attacks against it, then not only would there be no ius ad bellum justification for the use of force, but there would also be a requirement through IHRL to use this detention route rather than a military operation designed to kill.

The above is an attempt to provide a brief summary of some of the points in the article. For more detail on these and other issues addressed, I’m afraid you might need to read the rest.

Image: An Air Force F-15E Strike Eagle fires flares during a flight supporting Operation Inherent Resolve, June 21, 2017. Air Force photo by Staff Sgt. Trevor T. McBride