The Seemingly Inexorable March of “Unwilling or Unable” Through the Academy

The Seemingly Inexorable March of “Unwilling or Unable” Through the Academy

How does an international-law doctrine become conventional wisdom without actually having support in the practice of states? It starts with one article asserting the doctrine, but failing to defend it. Then another article makes the same claim, citing only the first article. And then another. And another. And so on — until no one remembers that the first article did not actually identify any state practice at all.

So it is with the “unwilling or unable” test, as indicated by an otherwise quite good new article in the Journal of Conflict & Security Law entitled “Jus ad Bellum and American Targeted Use of Force to Fight Terrorism Around the World.” Consider (p. 228):

With regard to the use of self-defence against private actors located in another state, two consequences flow from the requirement of necessity. First, state practice indicates that the exercise of self-defence against the private actor is conditioned on the inability or unwillingness of the authorities in the host state to stop the private actor’s activities.98 Obviously, if the host state both can and will stop the activities in question, it will not be necessary for the victim state to resort to the use of force.

I’ve left the footnote number in, because it refers to precisely one source: Ashley Deeks’ essay “Unwilling or Unable: Toward an Normative Framework for Extra-Territorial Self-Defense.” An essay in which, as I have pointed out, the author openly admits that she “found no cases in which states clearly assert that they follow the test out of a sense of legal obligation.” (The US and UK have formally endorsed the unwilling or unable test since Deeks’ article was published.)

To be sure, the new article elaborates a bit on the “support” for the unwilling or unable test. But none of that support involves the practice of states — nor does the article acknowledge the inconvenient fact that the Arab League (22 states) has formally rejected the test (post-9/11, even). Instead, it simply says this (p. 229):

The test is widely supported in the literature, and it is also mentioned in two 2013 UN reports by, respectively, the UN Special Rapporteur on extrajudicial, summary or arbitrary executions and the Special Rapporteur on the promotion and protection of human rights and fundamental freedoms while countering terrorism. It also features among a series of “Principles Relevant to the Scope of a State’s Right of Self-Defense Against an Imminent or Actual Armed Attack by Nonstate Actors” proposed by the former legal adviser of the United Kingdom Foreign & Commonwealth Office, Daniel Bethlehem.

“Instant custom”? How passé. Who needs state practice at all? And please don’t bore us by pointing out contrary practice by a bunch of benighted states in the Global South. All we really need are enough scholars, special rapporteurs, and former legal advisors in the Global North willing and able to endorse a particular doctrine and poof — customary international law.

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I agree that the so-called test is not a limitation of the inherent right of self-defense under customary international law or Article 51 of the UN Charter. But if the rockets are flying across the border, for that time at least, the foreign state is decidedly “unable.” Finally published: Operationalizing Use of Drones Against Non-State Terrorists Under the International Law of Self-Defense, 8 Albany Govt. L. Rev. 166-203 (215), available at


Thank you Kevin for drawing attention to the troubling methodology by which self-interested behavior of elite states is “legalized” through the assertion that it is “custom” (or at least attempted to be transformed into lawful behavior). Troubling too is how the meaning of “several’, “many”, and “frequent” are misappropriated to refer to the acts of two or three states. All states are equal but some are more equal, I guess. Still, Deeks, Kress, and Henriksen’s papers are great contributions to the thinking on this issue. It seems to me, however, that the value of their research and contributions could have stood independently (and perhaps even stronger) (e.g. Deeks articulation of substantive and procedural factors) without having to force “unwilling or unable” into a customary rule.

Thomas Welch

Great post. Soft law is undermining the development of badly needed, enforceable agreements by creating the dangerous, “poof” illusion of progress for political bodies to hide behind. Actual, documented conduct is then conveniently ignored for political expediency.

Tali Kolesov Har-Oz and Ori Pomson

Prof Heller, the sources the Ruys book (which is referred to in the previous post) relies upon to prove the Arab League rejection of the unwilling or unable test do not actually express a formal rejection of that test. Instead, the Arab League States condemned what they called Israeli “aggression” against Lebanon. This may relate to perceived dis-proportionality, lack of intensity for an armed attack and more. It does not necessarily expressly or implicitly indicate a rejection of the unable or unwilling test.

Tali Kolesov Har-Oz and Ori Pomson

Here is the link to the UNSC discussions cited by Ruys:
Here is a link to the text of the LAS resolution which is referred to in the discussions:

Tom Ruys

Kevin, Ori, Thank you for your interesting comments. What I wrote in the book (452-453) was simply that the League of Arab States condemned the Israeli aggression, not that it specifically rejected the unable and unwilling test. Overall, I found that back in 2006 (1) a majority of the international community regarded the self-defence claim of Israel as valid in principle, and; (2) that criticism focused almost exclusively on the obviously disproportionate character of Israel’s Operation ‘Just Reward’ (at 453). Accordingly, while I fully agree with Kevin that the need for a detailed and honest assessment of State practice and opinio juris is sometimes passed over too lightly, I do believe the 2006 Lebanon war offers a precedent that can validly be invoked to support the unable and unwilling doctrine. By contrast, several other incidents (e.g., Colombia’s Operation Phoenix) seem to reveal a more ambiguous position vis-à-vis the idea of a broadened right of self-defence against non-state actors (no longer dependent on any test of State imputability) – which is why I concluded that we seem to be witnessing an evolution de lege ferenda (!)of customary international law (530-531). What is particularly interesting with regard to the US-led operation against… Read more »

Tom Ruys


I don’t think ‘many States’ considered Hezbollah to be acting ‘on behalf of’ Lebanon. True, Israel suggested the 12 July attack was the action ‘of a sovereign State’, but at the same time Israel itself acknowledged Lebanon’s problem was mainly one of inability to disarming and dismantling Hezbollah.
Furthermore, numerous States, rather than holding it responsible for the attack, expressed sympathy for the Lebanese government (see also SC Res 1701(2006)).

It is fair to state that the Security Council debates do not provide explicit verbal support for the unable and unwilling doctrine as such, but when putting the pieces together the fact remains that (1) the Hezbollah attack was not imputable to Lebanon under the traditional law of State responsibility; (2) the majority of the international community did accept that Israel could rely on the right of self-defence, and; (3) the acceptance of the self-defence claim was inspired by the fact that Lebanon was unable to prevent cross-border attacks against Israel.