Home EJIL Analysis A Plea Against the Abusive Invocation of Self-Defence as a Response to Terrorism

A Plea Against the Abusive Invocation of Self-Defence as a Response to Terrorism

Published on July 14, 2016        Author: 

The use of force in self-defence against terrorist groups is one of the most controversial issues in the field of jus contra bellum today. Particularly since 9/11, several States have supported a broad reading of the right to use force in self-defence, as allowing them to intervene militarily against terrorists whenever and wherever they may be. A consequence of that conception is that any State could be targeted irrespective of whether that State has ‘sent’ the irregular (in this case terrorist) group to carry out a military action or has been ‘substantially involved’ in such an action, to use the terms of Article 3g) of the Definition of Aggression (annexed to GA Res 3314 (XXIX)) considered by the ICJ as reflecting customary international law. However, an even more substantial number of States do not seem to subscribe to this broad reading of the right to self-defence. The Non-Aligned Movement, for example, representing some 120 States, has regularly expressed its clear reluctance to adhere to this view. Thus, in February 2016, in an open debate before the UN Security Council on ‘Respect for the principles and purposes of the Charter of the United Nations as a key element for the maintenance of international peace and security’, the Non-Aligned Movement reaffirmed that ‘consistent with the practice of the UN and international law, as pronounced by the ICJ, Article 51 of the UN Charter is restrictive and should not be re-written or re-interpreted’ (S/PV.7621, 15 February 2016, at 34).

But what about international lawyers? The reaction on their part has been equivocal. Some have supported a broad interpretation of Article 51 of the UN Charter, focusing on the possibility to invoke self-defence against terrorists. Others argue in favour of a more ‘restrictive’ and classical reading of the Charter. Following this second line of reasoning, a plea against the abusive invocation of self-defence as a response to terrorism has been drafted by a group of scholars (available here). The aim of this post is to (i) explain in what context and how this plea was conceived, and (ii) briefly describe its main characteristics.

Context and Origins

The plea originates from two main events. The first was a panel on “The Fight Against ISIL and International Law” held in September 2015 during the ESIL Conference in Oslo. Five scholars participated in the panel: Théodore Christakis (as moderator), Karine Bannelier (‘External Intervention Against ISIS and the Legal Basis of Consent’), Nicholas Tsagourias (‘Self-defence and Non-State Actors’), Vaios Koutroulis (‘The Fight Against ISIS and Jus in Bello Issues’) and myself (‘The ‘Unable or Unwilling’ Theory; Has it Been, and Could it Be, Accepted?’). As the podcasts confirm, the legal basis of the armed intervention in Syria lay at the heart of the debate (the written and updated versions of those presentations have just been published in a special Symposium of the Leiden Journal of International Law (L.J.I.L.)).

A few months later, in April 2016, Philippe Lagrange organised a meeting in Poitiers about “The New Foundations of Recourse to Force (“les nouveaux fondements du recours à la force”). This meeting confirmed the existence of two conflicting trends: on the one hand, those who support an expansive definition of self-defence in the name of the war against terror; on the other, those who criticize this expansive definition not only as being contrary to the current state of positive international law but also as opening Pandora’s box, allowing for more unilateral military interventions around the world.

This persistent division among scholars is often ignored or at least minimized in other fora. In EJIL: Talk! blog posts, for example, it is regularly asserted that the broad conception of self-defence against terrorists is now generally accepted, or no longer challenged. Similarly, in a (particularly stimulating) workshop dedicated to ‘The Future of Restrictivist Scholarship on the Use of Force’ published this year in the L.J.I.L., it seems to be taken for granted that the ‘restrictivists’ ‘are increasingly isolated’ .

In view of the above, it was suggested to colleagues and friends present at the Oslo and/or Poitiers mentioned above that we write a text expressing our reluctance to endorse the expansionist conception of self-defence that seems to have spread across the political and legal landscape. The aim was not to challenge the legality of the war against ISIL as such (actually, several among us supported the merits of a military intervention against ISIL), but rather the legal argument put forward by some States, mainly the US and several European States after the events of 13 November 2015. A first draft, in French, was prepared by me and this was supplemented and in parts substantially amended by my colleagues (Karine Bannelier, Théodore Christakis, François Dubuisson, Nabil Hajjami, Philippe Lagrange, Franck Latty, Vaios Koutroulis and Anne Lagerwall). Once the French version was finalised, it was translated into English and circulated among a number of colleagues for signature. To be honest, the success of the plea exceeded our expectations: after only ten days, the plea had been signed by more than 200 international lawyers from many parts of the world, professors in Argentina, Australia, Austria, Bahrain, Belgium, Brazil, Burundi, Cameroon, Canada, Columbia, Costa Rica, Chile, China, the Democratic Republic of Congo, Cyprus, Finland, France, Germany, Greece, Iran, Israel, Italy, Japan, Kazakhstan, Kuwait, Luxembourg, Mauritania, Netherlands, Portugal, Romania, South Africa, Spain, Switzerland, UK, Uruguay, and USA. One can find among the first scholars who signed the plea many specialists of jus contra bellum, as well as several other well-known international lawyers. This is particularly pleasing as a question as fundamental as the scope of self-defence in contemporary international law is not an issue reserved only to jus contra bellum specialists: every international lawyer can take a position on this topic.

Substantial Characteristics of the Plea

The plea does not deny as such the possibility of using self-defence in the context of the fight against terrorism; it simply recalls that such a resort to force constitutes an exception to the prohibition of the use of force in international relations and consequently must be in conformity with the conditions laid down in the UN Charter and positive international law. On this basis, it sets out two main ideas, both of which could be considered as rather classical and orthodox.

The first is that self-defence must be considered as a last resort, only relevant when other (peaceful or coercive) means are not available: “international law provides for a range of measures to fight terrorism. Priority should be given to these measures before invoking self-defence.” Such measures are: first, peaceful measures such as police and judicial cooperation; second, military measures with the cooperation of the territorial State; third, referring the situation to the Security Council: “aside from cases of emergency leaving no time to seize the UN, it must remain the Security Council’s primary responsibility to decide, coordinate and supervise acts of collective security”; fourth, in case the first three possibilities are not available or have failed, recourse to the unilateral use of force based on self-defence.

The second main point of the plea is to identify the conditions for validly invoking self-defence, once the means described above have been exhausted. In this regard, the text states that:

This may occur either where acts of war perpetrated by a terrorist group can be attributed to the State, or by virtue of a substantial involvement of that State in the actions of such groups. In certain circumstances, such involvement may result from the existence of a direct link between the relevant State and the group. However, the mere fact that, despite its efforts, a State is unable to put an end to terrorist activities on its territory is insufficient to justify bombing that State’s territory without its consent.

With the exception of Article 51 of the UN Charter, the text does not mention any source or reference. This is because the plea intends to put forth a general legal position and is neither a detailed scientific study nor a review of existing case-law and literature. By focusing on the “attribution” and “substantial involvement” criteria, the text nevertheless implicitly refers to Article 3g) of the Definition of Aggression.

Although the text of the plea is open to several interpretations (as is every legal text), it excludes very broad readings of the right to self-defence. For example, it would be difficult —if not impossible— to reconcile the text with the ‘unwilling or unable” test as used by some States and scholars recently.

Finally, it must be repeated that the text does not address the issue of the legality of the war against ISIL as such. The plea states explicitly that the signatories are not “oppos[ed to] the use of force against terrorist groups as a matter of principle.” Indeed, the basic purpose of the plea is rather to contest the legal argument invoked by some States and scholars to justify this military campaign i.e. an extensive view of a right to self-defence that can be exercised against any country even if the government of that country would be ready to consent to a multilateral military operation under the supervision of the Security Council.

*          *          *

A final word: the purpose of this initiative is not to “prove” that the classical “restrictivist” approach to self-defence necessarily reflects the majority position in contemporary scholarship. However, in view of the current list of signatories of this plea —and whatever the final number and identities of the signatories may be— it is henceforth clear that the broad conception of self-defence that has been proposed by certain scholars during the last 15 years is not “universally” or “overwhelmingly” accepted. States’ representatives, but also every international lawyer, should at least be aware of that.

Thanks to Vaios Koutroulis, Théodore Christakis and Marco Benatar for their valuable help in the finalization of this text.

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26 Responses

  1. Although not a signatory of the plea, I very much welcome Olivier’s clarification. Those are very serious matters and, as lawyers, we should always foster professional integrity. However, the fact that such clarification has been made is not only useful, but also very much telling from a methodological and deontological point of view.

    To be honest and open about it, and in true friendship with Olivier, the other initiators of the plea and the signatories, I was baffled by the timing of the plea, but not surprised by the use that was made of it.

    The plea was published in “Le Soir” (the most widely circulated newspaper in French-speaking Belgium) and published in that newspaper on the very day (30 June) the Belgian Parliament held a debate on the involvement of the Belgian air force in the fight against ISIS in Syria. I cannot see this timing as accidental and assume it was openly stated to the signatories.

    At the House of Representatives, the speaker for the Green party quite literally unrolled the list of the 176 signatories (at the time) as testimony of the fact that bombing ISIS in Syria was in breach of international law: see the verbatim of the meeting here, at page 44 by Benoit Hellings (Ecolo), n°06.31

    Of course, the initiators of the plea who submitted the text to the newspaper are not responsible for what politicians make of it. But it is clear that Mr Hellings publicly relied on the signatories’ scientific authority to contest the decision of the Belgian government to commit F-16 and to bomb ISIS in Syria, irrespective of Syria’s consent.

    Each of us is free to engage in public debate and develop whatever personal views one may have as an expert. But I like to think that we have a specific methodological and deontological duty of care when we call upon our colleagues to commit their names on a text that is going to be made public and possibly used in the public debate.

    Olivier tells us that the plea is a “legal text”, that it is therefore open to different interpretations, knowing however that it “does not address the issue of the legality of the war against ISIL as such.”

    Methodologically, I am not sure such a text can be considered as a “legal text” simply because it is drafted and signed by lawyers and is about legal matters. Therefore, the excuse of open interpretation does not really stand in light of the true doctrinal nature of the text.

    Deontologically, it seems to me that the silence of the plea on the “legality of the war against ISIL as such” is a trap in which some signatories may have inadvertently fallen. I think the Green party MP was quite right to read the plea as he did, since this is the stated view of its initiators and it was how the text was presented to the press: the use of force against ISIL in Syria cannot be justified under any existing UN resolution, nor on the basis of self-defence, and, in the absence of Syria’s consent, it is in breach of international law — in other words and in substance: call the F-16 back home and stay out of the air space and territory of Syria.

    I was not asked to sign the plea and therefore (but not only for that reason) did not sign it. Like most signatories, I am (of course) also against the abusive invocation of self-defence — or for that matter, against the abusive use of any right.

    It remains unfortunate that the apparent benign title and, to some extent, content of the plea could be used in a way that was not made explicit by its authors. It is problematic if ambiguity of the draft was intentional, but also if it was not. I submit that the authors would have been better inspired by something as explicit about ISIS and Syria as the famous “We are teachers of international law”, published in the Guardian at the time of the 2003 war in Iraq (

    Let diplomats indulge in ambiguity and practice clarity between us: my plea is against collective doctrinal pleas that do not clearly state what they mean in the context of their drafting and circulation.

  2. Jordan

    One main problem is the assumption that a necessary response to nonstate actor armed attacks emanating from the territory of State B is a responsive attack on State B. Another is the assumption that a restrictive read of Article 51 necessarily prohibits targetings of nonstate actors engaged in cross-border violence and that customary or “positive” international law prohibits self-defense measures claimed during The Caroline incident like the targeting of a nonstate actors shore battery.

  3. Jordan

    First premise, an armed attack and probable process of armed attacks is underway. Does anyone really believe that the opinio juris of humankind is that a terrirorial boundary is more important than other human values like the human rights of victims of ongoing NSA armed attacks to life and personal security (which is so often absent from some discussions)? What if the attack in Nice was not, as seemingly likely at this momment, at the hands of an ISIS wanabe, but was ordered from Syria? Would the opinio of humankind actually embrace a form of territorial immunity?
    Nothing in the language of Article 51 of the Charter precludes responsive force to ongoing armed attacks by nonstate actors, nor is practice opposed.

  4. Raphael Van Steenberghe van Steenberghe

    Personally, I was ready to sign the plea. I agree that a state victim of an armed attack by non-state actors, in particular terrorists, (or those helping that state) must exhaust all other available means than use of force in self-defense (including referral to the UNSC, seeking consent of the state where the terrorists are located, relying on the military action of that state) before acting in (collective) self-defense. It is only when those alternative means are not lawful or not effective enough to protect the victim state against the armed attack that this state (or those helping it) may resort to (collective) self-defense. In my view, this is per se required by the condition of necessity of the law of self-defense.

    Yet, I did not sign the plea because of paragraph 5 thereof, in which it seems to be stated that self-defense can only be exercised in reaction to an armed attack by a state. This position (if I understand it correctly) excludes the right to act in self-defense in response to armed attacks committed by non-state actors only (i.e. which cannot be attributed to a state or in which no state is substantially involved), although it is at least a debated issue. I did not want to endorse such a position. Actually, I am not sure that all the signatures to the plea can be counted as clear scholarship expressions of approval of that very position. It is indicative that the plea has been signed by scholars who do not share such position in their own writings or, at least, adopt a more nuanced stance on the matter. I guess that they would not want to be considered as supporting that legally strict position without any further nuance.

    This suggests that the plea is not (and should not be considered as) a scientific paper which would have been submitted to other scholars for scientific approval. It is rather a general political warning addressed to states when they decide to resort to force abroad against terrorists. I guess that it is in that sense that many scholars signed the plea. From a methodological point of view, I therefore think that it should not be used for scientific/academic purpose, especially for claiming that all the legal positions expressed therein, including the aforementioned controversial one, are necessarily supported by the signatories.

    I also doubt that one can infer, from the number of signatories to this plea, any reliable conclusion on the debate concerning the current extend of the restrictivist scholarship approach to self-defense, which supports the requirement of an armed attack by a state, in particular whether this position is marginal or not in legal literature. To give any weight to that plea, one should also explain to how many people it has been submitted (and, thus, how many have refused to endorse the position at stake), whether it has been submitted to scholars known as challenging this position, etc. The weight of the scholarship defending the abovementioned view is necessarily relative. One can thus only assess it in relation with the positions held by all scholars around the world. Obviously, we will never organize a worldwide plea over this question. Hence, I think that a scientific approach would consist in analyzing, from the papers of scholars (and, thus, with their nuances and in-depth analyses), whether a vast majority of them denounce the disputed position or not. To the contrary, deducing conclusions from a plea to which many signatories may have subscribed for various reasons (not always scientific ones) and of which we do not know whether any and all details are endorsed by the signatories would seem hazardous to me.

  5. Thanks all for your comments.

    Pierre, I understand you are baffled, like you seemed to be in Oslo and in the other occasions when we talked about this issue. However, this time, and reading your comment, I’m not sure I really get your point.
    In the post, I clearly explain the origins and the objective of the plea: to counter the (very common) argument according to which an expansive interpretation of self-defence would be broadly (if not universally) accepted by international lawyers. Do you suggest the presentation I wrote for EJJLtalk! would be misleading or at least partial in this regard? In other words, do you suggest I had a ‘hidden agenda’ while launching this initiative? Do you think I seriously believed that such an endeavour would convince the Belgian government to abandon the decision it had announced long before the 30th of June? Do you actually think that the support the green party (or one of its representatives) at the domestic level was one of my concerns, something that motivated the launching of the plea rather than my own academic concerns? And on a broader perspective, is it inappropriate for legal scholars to take public positions knowing that they could be used by political authorities in a way or another? Against this backdrop, was it inconvenient —especially for a ‘plea’— to send the text to several newspapers and media in Belgium and abroad?
    Finally, concerning the signatories of the plea, do you seriously think they didn’t know that this kind of text could be used by those who stand against the abusive invocation of self-defence ‘as a response to terrorism’ (and not in general)? Did they prove to be naïve by signing the plea? Or were they fooled? Honestly, I was shocked by your reaction. Rather arguing on the merits, it is implicitly (but clearly) pointing to a lack of honesty on my behalf, and to an issue of deontology. Such a critic sounds very serious, especially when uttered by a ‘friend.’

    Jordan, I personally think it is difficult to deny that bombing the territory of a State is a use of force against such a State… And, if you attack a State, you simply must be able to invoke an argument vis-à-vis this State. Concerning your second comment, I’m not sure we disagree: if any ongoing attack was ordered by the Syrian authorities, Article 51 obviously would allow the victim State to riposte. Finally, and of course, territorial integrity isn’t more important than other human values, especially human rights. This is precisely why, in my opinion, cooperation between States against terrorism, possibly under the supervision of the Security Council, should be privileged.

    Raphaël, I know and very much respect your position. Your comment confirms that the text does not concern the legality of any particular war as such, but rather a general conception and interpretation of self-defence. And, in relation to that, I’m of course not surprized that you disagree with paragraph 5 (this is why I didn’t write to you and let you decide after having read the plea when published on the net). Some colleagues refused to sign the plea precisely because of this paragraph. Others, sometimes after some exchanges of emails, decided to sign. A vast majority of the signatories simply welcomed the appeal and sign it without any comment. I strongly believe they all knew what they did. Consequently, I think you cannot just label this common position about the scope of the right to self-defence, framed in legal terms, and shared by many honourable colleagues (including some famous specialists of jus contra bellum), as a mere ‘general political warning’ (!?). The signatories are all professional lawyers and are perfectly able to recognize a legal text (ie a text expressing a legal position and a legal reasoning), especially in the context of a sensitive legal controversy which is evoked in the first lines of the plea and that no jurist can ignore. At the same time, and I tried to be clear about that in my presentation above, it would be excessive to argue (and I’ve never and will never argue) that this plea would prove that a ‘restrictivist scholarship’ represents a ‘majority.’ What is sure, however, is that this restrictivist position cannot be considered as inexistent or marginal, in view of the number and of the identity of the signatories. Finally, and concerning the interpretation of the plea, I just would like to draw your attention about this phrase: ‘In certain circumstances, such involvement may result from the existence of a direct link between the relevant State and the group.’ In my view (but everyone is of course free to interpret this text), this could be seen as a very nuanced legal position able to tackle adequatly some problems raised by you and other scholars. And perhaps this particular phrase could explain why some scholars you evoke have signed the plea.

  6. Dear Olivier, thank you for sharing your thoughts and for your interesting article. I must say that I agree with parts and disagree with others. Firstly, I do agree that other means must be exhausted before resorting to force. This is a must. However, I side with Jordan. I think it is artificial to say that an attack that targets non-state agents is an attack *on* the State simply because they are in its territory. This would amount to say that any killing taking place somewhere is an attack on the State, or that attacking nationals of a State automatically implies that the State is attacked. That is not true, and note that territory and nationals are both elements of the State. So I think Jordan is right, the fact that an attack takes place in a territory does not imply that the State is attacked. Another thing is whether such attack infringes territorial integrity. It may, but a proportionate analysis could lead to considering that other values, as Jordan indicates, may eventually make operations lawful. Just my thoughts from Colombia. Thanks for the discussion.

  7. Jordan

    Olivier: bombing the territory is not what is involved in bombing ISIS.

  8. […] en un análisis de proporcionalidad. Este dilema se refiere a un debate abierto por Olivier Corten aquí, en el que él defiende que atacar a un grupo no estatal ubicado en un tercer Estado necesariamente […]

  9. Jordan

    Or it is not the intent of the self-defender.
    Also, I may mot have been clear about ordered from Syria b/c I meant to pose the circ. where ISIS ordered the attack from its location in Syria.

  10. Marty Lederman

    Olivier: Thank you very much for this. As a relative newcomer to this question, what befuddles me about this initiative is that it appears to be designed simply to demonstrate that there are many scholars around the world who are of the view that the phrase “armed attack” in Article 51 does not encompass attacks by a nonstate actor, where those attacks are not in some meaningful sense attributable to the state in which the NSA has taken refuge and from which it launches the attacks.

    Strikingly, the statement does not, for example, attempt to defend this reading the Charter, let alone demonstrate that any states, or most states, support it. But then why go to such efforts to demonstrate how many scholars accept that view?

    In your post, you write that the “division among scholars is often ignored or at least minimized in other fora. In EJIL: Talk! blog posts, for example, it is regularly asserted that the broad conception of self-defence against terrorists is now generally accepted, or no longer challenged. Similarly, in a (particularly stimulating) workshop dedicated to ‘The Future of Restrictivist Scholarship on the Use of Force’ published this year in the L.J.I.L., it seems to be taken for granted that the ‘restrictivists’ ‘are increasingly isolated.’”

    I was taken aback by this. In the EJIL: Talk! posts and comments of which I’m aware, for example, many of us have claimed that the “broad” conception is now generally accepted *by states.* And it is also accepted by many scholars, including, I’d wager, a majority of those here in the U.S. who have studied such things. But I have not seen anyone claim that the “restrictive” view is defunct *among academics.* To the contrary, the fascinating thing–the thing that has taken me aback, in any event–is that so many scholars adhere to that view, even though virtually no states do (and even though it would mean a repudiation of the Caroline). That is to say, what I thought we were remarking upon was the surprising fact that the restrictivist view remains so prominent *in the academy,* even though it has little or no purchase outside the academy (or in the text, or history of state conduct).

    All of which is to say that it appears to me that you’ve proved a fact about a divergence of academic views that (as far as I know) no one was challenging. But perhaps I’ve overlooked something. Thank you in advance for any clarification.

  11. Raphael Van Steenberghe Raphaël van Steenberghe

    Olivier, thanks for your response. Just three reactions:

    1) I am still convinced that those who signed the plea did not all necessarily do so with the intention to endorse all the legal positions expressed therein, especially the controversial one on the scope of the notion of armed attack under Art. 51 of the UN Charter. I personally know honorable lawyers who did sign the plea but not with that intention. They did sign the plea not as a scientific paper for scholarship purpose but because of the general commendable aim pursued by that plea, i.e. warning states not to resort too easily to force (in particular by unilateral actions in self-defense) when countering terrorist threats; but they had not analyzed in-depth or did not endorse any and all legal arguments exposed in the plea. Sometimes, it happened because they were not specialists of jus ad/contra bellum and could not therefore be aware of all the nuances of the debate in that field, particularly on the law of self-defense and the notion of armed attack. In that sense, as you rightly say, these honorable lawyers perfectly knew what they did : signing a plea in a given political context for warning against any abuse of the use of force in response to terrorism, rather than giving a comprehensive opinion in a scholarship debate on the law of self-defense.

    2) I never argued that the plea was used to prove that the restrictive approach to self-defense represents a majority. In any case, it would not have been possible since it would have implied to know the opinion of all international lawyers. Some scientific conclusions, even limited, on the state of legal scholarship on self-defense seem nonetheless to have be drawn from the plea when it is stated in the post : “However, in view of the current list of signatories of this plea […] it is henceforth clear that the broad conception of self-defence that has been proposed by certain scholars during the last 15 years is not “universally” or “overwhelmingly” accepted”. I guess that this broad conception includes the right to act in self-defense in response to armed attacks by non-state actors. It is also indicative that the plea was motivated, as you indicate in the post, inter alia by the will to counter/respond to the idea – developed in blogs like EJIL talk! or in symposiums as the one you mention in the LJIL – that the orthodoxy on the law on the use of force has dramatically switched in legal scholarship from a restrictivist to an expansionist perspective, in particular that the majority of the scholarship now agree that self-defense can be exercised in reaction to imminent armed attacks and in reaction to attacks by non-state actors. Anyway, the essential aim of my comment was to emphasize that one must be very cautious with such plea and not draw any conclusion from it about the state of current scholarship, especially on this very complex issue of the scope of the notion of armed attack under Article 51 of the UN Charter. Such conclusion could only be drawn from an objective survey of scholars’ scientific writings on that issue (see e.g., for an attempted survey of English and German language articles, the paper of J. Kammerhöfer in the Oxford Handbook on the Use of Force in International Law).

    3) I indeed noticed the phrase “In certain circumstances, such involvement may result from the existence of a direct link between the relevant State and the group”. However, “such involvement” must still be “the substantial involvement of [a] State”. The armed attack must therefore still be an armed attack by a state (even indirect), which excludes the right to act in self-defense in response to attacks committed by non-state actors only (i.e. which cannot be attributed to a state or in which no state is substantially involved). This phrase also implies softening the conditions for the existence of an indirect armed attack by a state. This may be dangerous as this can more easily justify states responding in self-defense to target that (aggressor) state – rather than only the non-state actors. It would be better to recognize in that case the right to respond in self-defense to armed attacks by non-state actors since, as supported by many scholars, the self-defense reaction can only be exercised in that situation against the non-state actors. But this is another story…

  12. Thanks all for your contributions to the debate. At this stage, I’d like to add some indications about the content and the status of the plea. Of course, what follows only reflects my own personal opinion. As I mentioned in the post above, every text is open to various interpretations, perhaps especially when expressing a compromise shared by more than 250 specialists of international law coming from all over the world.

    Concerning the content and scope of the plea, the first think to point out is that it does not exclude self-defence to counter an attack against a non-State actor. Actually, it simply refers to the criteria contained in the definition of aggression accepted by all UN Member States and used by the ICJ to interpret Article 51 of the UN Charter in several occasions. According to this definition, any ‘attack by the armed forces of a State of the territory of another State’ or ‘bombardment by the armed forces of a State against the territory of another State’ are clear examples of a ‘use of armed force by a State against the sovereignty, territorial integrity or political independence of another State.’ When, like it happens in Syria, you bomb the territory of another State without the consent of its government, kill dozens or hundreds of its nationals, destroy some of its buildings and infrastructures (like oil facilities), causing millions of $ of damages, is it really serious to contend that you simply do not ‘target’ or ‘attack’ that State? Honestly, I don’t think so, and I’m convinced every State in the world bombed by another State will share my view. Another aspect of the plea is to recall the conditions laid down in Article 3g) of the definition of aggression, by enouncing two hypothesis in which self-defence could be used against another State: either this State has ‘sent’ a non-State group to perpetrate an act of aggression (and in this case this State is itself the author of this particular act), or it has been ‘substantially involved’ in the activities of this group. In this latter hypothesis, the act of the non-State group cannot be attributed to the State, but this State is directly responsible for its ‘substantial involvement’, which would be equivalent to an act of aggression in some circumstances. If one of those two conditions is met, self-defence can justify a military riposte if ‘necessary’, which implies in this kind of situation some exhaustion of alternative measures. All those conditions don’t come from any academic imagination, but reflect texts (especially the definition of aggression), case-law (especially by the ICJ) and the position of (at least a significant number of) States (in the post, I mentioned a NAM statement in 2016, but many similar other ‘restrictive’ statements can be found).

    Concerning the status of the plea, well, actually, I don’t really understand the problem. Of course, no-one can know the intention of every of the hundreds of signatories of the plea. However, this plea is openly and undoubtedly a text expressing a legal interpretation about the scope of self-defence, signed only by professional international lawyers. The letter sent to the first list of signatories mentioned that the plea would be published in a journal of international law, the Revue belge de droit international. In this context, and in good faith, it can reasonably be considered that those who signed share the position expressed in the text. Of course, everyone is free not to refer to it, or try to minimize it by various means. Personally, I found it very interesting to observe that a rather restrictive conception of self-defence is not only supported by a substantial number of States but also by a substantial number of scholars, contrary to what is regularly contended in various debates, either in EJILtalk! or not…

  13. Marty Lederman

    Thank you again, Professor Corten. I don’t think there’s much disagreement that the host state can only be deemed to have engaged in an act of aggression if, at a minimum, it was “substantially involved” in the activities of the NSA that launched the armed attack. Article 51, however, does not, by its terms, require an act of armed aggression by the host state in order to justify what would otherwise be a prohibited use of force against its territorial integrity–instead, it requires an “armed attack”; and the common law of the “inherent” right of self-defense also requires that the responsive use of force be necessary and proportionate to stopping/preventing such armed attacks, rather than an indiscriminate use of force against the host state. There is nothing in the text, however, to suggest that such an armed attack might not come from a nonstate organization that is using the host state’s territory for refuge, regardless of the involvement of that host state — just as the U.S. was not responsible for the actions of the rebels that prompted Britain’s use of self-defense against the Caroline. Of course, the responsive use of force must be tailored to stopping such attacks. That’s why, in the cases in question, it would be improper to attack the forces and other military targets of the host state: the use of force in self-defense must be directed to the NSA that presents the threat of armed attacks. As you properly note, this does not mean that the state’s territorial integrity is not breached — it certainly is. But Article 51 describes a narrow circumstance in which such a breach is permissible.

    We now know that many states support this view–reflected in both their actions and their words.

    You repeat the idea that a more “restrictive conception of self-defence”–one in which the armed attack must in some significant sense be attributable to the host state–is supported by “a substantial number of scholars, contrary to what is regularly contended in various debates.” Once again, I’m not aware of debates in which anyone denies that many scholars hold this view–certainly not here on OJ.

    More importantly, you also represent that this view is supported by “a substantial number of States.” Yet you offer no evidence of this, save for a recent statement of the Non-Aligned Movement that “consistent with the practice of the UN and international law, as pronounced by the ICJ, Article 51 of the UN Charter is restrictive and should not be re-written or re-interpreted.”

    I don’t know anyone, however, who disagrees with that statement, at least at that level of generality: It’s true that Article 51 of the UN Charter is restrictive–well, it’s narrow, anyway (it recognizes an exception — the restriction is in Article 2(4), and in the constraints of necessity and proportionality) — and should not be re-written or re-interpreted (indeed, that’s why I think it’s difficult to justify adding an implicit term, e.g., “attributable to the host state,” to Art. 51). As far as I know, however, none of those nations have specifically rejected the view that the inherent right of self-defense confirmed in Article 51 can be triggered by a nonstate actor’s armed attack for which the host state is not responsible. Have *any* states, for instance, complained that the current use of force in Syria against ISIL, by many other states, is a breach of the Charter — a view that would necessarily follow if the position of the signatories were correct?

  14. I’m afraid it is difficult to develop the debate… ‘Article 51 can be triggered by a nonstate actor’s armed attack for which the host state is not responsible’, I fully agree with that. But if you bomb a State you must me able to invoke self-defence vis-à-vis this particular State. According to me, it is not only what can be deduced from texts; it is simply common sense. Concerning the position of States, please consult my book (The Law against War, 2010, a more recent version exists in French, 2014), among others the reactions by States after the 2004 Wall advisory opinion (in which the Court reaffirmed the inter-State character of Article 51). You will also understand more precisely what is the legal position supported by the NAM for decades (see particularly the debates surrounding the 60the anniversary of the UN Charter). Concerning the ISIS crisis, just consult the documents mentioned in the post (the Oslo panel and, later, the LJIL 2016). Concerning Article 51 (which is indeed very vague in that regard, even if no State even imagined in 1945 that self-defense could be invoked against another subject that the author of the armed attack), taking into account the definition of aggression (as the ICJ systematically did when it interpreted Article 51) could be helpful. I guess that will not convince you, but at least you could hopefully accept that there is a deep disagreement between scholars (I’m happy to observe that you are aware of it, but believe it is not the case of everyone writing on EJILtalk! – on OJ, I don’t know) and States about this…

  15. Marty Lederman

    Believe me, I certainly do “accept that there is a deep disagreement between scholars”! Indeed, the whole point of my modest interventions here (sorry, I meant to refer to EJIL Talk!, not OJ; but the conversation is on both sites) is to try to figure out *why* there has been such disagreement, when the “restrictivist” view appears to me (a conceded newcomer) to be so deeply counterintuitive and contrary to text, state practice, canonical pre-Charter history, and opinio juris.

    I’ve printed out the LJIL articles and look forward to reading them for further understanding. For now, however, I’ll simply press on two things in your latest comment, because I think they begin to illustrate why the two sides in this debate are so often speaking past one another.

    First, you write that it is “simple common sense” that “if you bomb a State you must me able to invoke self-defence vis-à-vis this particular State.” Well, yes, I agree — *if* your bombing consisted of actions designed to weaken that state, or its military capabilities. But if, instead, your bombing is tailored to harming a third party that has taken refuge in that state, and that has attacked you from that refuge, why would “common sense” dictate that the self-defense must be vis-a-vis the state’s armed attacks, in particular? Imagine, for instance, that you and your neighbor get along famously, and that you both honor the general rule that you not harm the “territorial integrity” of one another’s backyards. One day, however, a third party encamps on your neighbor’s yard and begins shelling your house. Your neighbor is unable to do anything about it (perhaps she is fearful for her own safety), and yet she also asks you not to respond, because any such response will inevitably damage her real property (even though that would not be your intent or the focus of your response). Should the law prohibit you from doing anything to stop the third-party attacks, as long as your response is tailored to that objective? Why would anyone agree to a rule that would allow you to respond on your neighbor’s territory if she is responsible for the attacks, but not if she isn’t? Common sense, that is to say, appears to me to point in the direction of the text of Article 51 (which includes no such distinction), not against it. (Of course, one might argue that you should not be able to use force unilaterally in *either* case — that you must leave that job to the police (i.e., the UN). But if such resort is not going to be required in the case where your neighbor herself attacks, it’s not obvious to me why the rule would be different when it’s the neighbor’s uninvited squatter who is doing the attacking.)

    Second, you write that “no State even imagined in 1945” that self-defense could be invoked in these circumstances. Yet these circumstances are precisely the case of the Caroline, which I understood to be the canonical example of “inherent” self-defense that Art. 51 was designed to preserve (assuming, of course, that the British, not the Americans, were correct about the question of necessity in that case). What I find difficult to imagine is that *any* state, in 1945, imagined that the Art. 51 right of self-defense would not cover self-defense against the Canadian rebels in 1837, just because the U.S. was not responsible for their attacks on Canada.

  16. Well, thanks, but this is obviously an endless discussion… I’m not sure that an example of (private) domestic law could be transposed, but if it could, I would say, as you suggested yourself, that the proper way to proceed would be to call the police… (I’m not sure, however, this will learn us anything about our issue). Concerning the Caroline, I’ve always been puzzled to observe that those who consider that international law must be adapted to new circumstances of the 21st century consider that an exchange of letters that took place in 1837, between two States, at a time when no system of collective security existed (and, according to many, no genuine prohibition of the use of force existed either), should govern international relations today and could be opposed to all the UN Members… Once again, I personally prefer to invoke contemporary texts accepted by all States, like the definition of aggression.

  17. Marty Lederman

    Fair enough — I deeply appreciate your extended engagement on this question here, and I hope that there is occasion to continue the conversation in other fora. I’ll close where you did–with the suggestion that this question be addressed with reference to “contemporary texts accepted by all States, like the definition of aggression.”

    I agree that the definition of aggression can be very valuable in determining whether the armed conflict is attributable to the host state. I suppose the principal point I’ve been stressing, however, is that that question is distinct from, and not determinative of, the question of which attacks can trigger the inherent right to use force in self-defense within the host state, per Article 51. I can’t put the point much better than Prof. Tsagourias does in his contribution to the Leiden Journal symposium:

    [The] most important flaw [in the “attribution” approach] is conceptual
    because it conflates the law of state responsibility with the law on the use of force; two legal regimes with different rationales, content and exigencies. The use of force regime is a regime of primary rules which set out the circumstances and conditions under which force can be lawfully used in international relations. For example, Article 51 of the UN Charter establishes a legal entitlement to use force when an armed attack occurs irrespective of its author or of issues of responsibility. The law of state responsibility instead sets out the conditions and methods for holding states responsible for violations of their international obligations. Attribution in the law of state responsibility is thus the mechanism according to which non-state acts are transformed into state acts or, to put it in different terms, non-state acts are
    ‘subjectivised’ for purposes of responsibility. It is for this reason that the law of state responsibility requires compelling state input into non-state acts or non-state actors namely, in order to distinguish private from public (state) acts.

    Because of the different content and rationale of the two regimes, questions arise as to the function and propriety of such inter-systemic transfer. More specifically, questions arise as to why secondary rules of attribution should determine the content and scope of the primary rules on the use of force.

  18. Jordan

    Olivier: we should note that the “definition” aggression is expressly conditioned by the need for a violation of the Charter, which “begs the questions” regarding both 2(4) and 51. It does use a substantial involvement test regarding attribution of NSA armed attacks to a state for permissible responsive force against the state (a test that the Nicaragua opinion referred to, as opposed to the effective control test regarding attribution for war crimes by the NSA).

  19. Raphael Van Steenberghe Raphaël van Steenberghe

    Again, many thanks, Olivier, for your response.

    Just two short and last remarks:

    1 – If I read it correctly, the plea does exclude the right to act in self-defense in response to attacks committed by non-state actors only (i.e. which cannot be attributed to a state or in which no state is substantially involved). This comes from the terms “only lawful” and “either … or” used in paragraph 5.

    2 – In the same way as one must be cautious when inferring the opinio juris of states from their behavior on a specific legal question related to use of force (as, I think, you are), one should similarly be cautious when inferring the legal opinion of scholars in that matter, especially from documents which are not scientific papers. Finally, in my view, this more fundamentally raises the interesting methodological question (and I know that you are very sensitive to questions of such nature) of the identification of the “opinio juris” of scholars from their conducts, declarations or other behaviors. This could be the subject of a paper!

  20. Marty Lederman

    Raphaël, I’m genuinely curious: Is there any particular reason that we should care about some sort of definitive “opinio juris” of scholars? I find it a bit odd, and perhaps even disconcerting, that we appear to be engaged in a debate about the number or percentage of scholars who embrace one view rather than another, to the point where we’re counting noses without regard to any of the actual arguments in support of the competing views (arguments that are not, for example, offered in “the plea” at issue here). A classic case of the appeal-to-authority fallacy, no? (There’s a bit of this occurring with respect to the Chilcot Report’s account of Lord Goldsmith, too, e.g, “he must be wrong in his reading of Resolution 1441 because 95% of British scholars disagree with his conclusion.” Goldsmith might well be wrong (just as the signatories to the Plea might be right); but if he is, it’s not because most scholars have rejected his view. One has to attend closely to the merits of their arguments — which, to be fair, many of them have offered, see

  21. Raphael Van Steenberghe Raphaël van Steenberghe

    Marty, I do not go into the substance in this discussion as I know very well Olivier’s position on the issue at stake and we already had the occasion to exchange our views several times in detail on that issue, on EJIL talk! (see e.g. and elsewhere. In addition, such issue has been debated in-depth between scholars in previous discussions on EJIL talk!. I therefore wanted to focus my comment on some methodological aspects.

  22. Jörg Kammerhofer

    This is a brief comment on the sociology of scholarship in connection with this declaration: for a while now, it has appeared to me to be the case that – amongst continental European international legal scholars – the likelihood of a wide reading of self-defence in connection with non-state actors is higher the younger the scholar is and vice versa. This does not exclude outliers in both directions, of course, but those socialised as international lawyers before the events of 11 September 2001 seem to be more likely to favour an narrow reading and those socialised afterwards seem to favour a wider reading. The names on the list of signatories seem to confirm this anecdotal feeling. Also, the same can probably not be said with respect to other questions of the law on the use of force, foremost the question whether military action against Iraq in 2003 was legal.

    Olivier, Raphael, do you believe that this is an accurate representation of the age distribution of opinions?

  23. Roger O'Keefe

    Dear Jörg
    Are you calling me old?
    Yours crustily

  24. Thanks all. The main point remains what appears to me as a dilemma. On the one hand, no one deny that force could be use against non-State actors having perpetrated acts of ‘such gravity as to amount’ to an act of aggression. Actually, self-defence (without being excluded as such) is not really useful in that regard, however, as there is no prohibition to use force against non-State actors. On the other hand, if you attack not only a NSA but a foreign State (i.e. if you bomb its territory without cooperating with it, causing damages and victims among its nationals, as a recent coalition attack did), self-defence will be useful, but you’ll have to establish a certain responsibility by the targeted State itself. Sorry to repeat that, in my view, it is simply logical. By the way, I don’t see any confusion, at this stage, between jus contra bellum (and particularly art 3g) of the definition of aggression) and the law of international responsibility. The substantial involvement criterion, particularly, is relevant without any need to attribute the acts perpetrated by the NSA (and, more generally, art 3g) is a lex specialis applicable as such to address that sort of problem, as the ICJ confirmed).
    Finally, concerning the status of the appeal, just take note more than 270 international lawyers have signed the plea so far. As our discussion confirms, this plea contains a specific legal position and traduces a specific legal reasoning. In my view we should take this seriously into account when we try to determine what is the current view on this topic in the existing scholarship. The signatories come from very different countries, with different legal cultures, and different ages. Many ‘young’ international lawyers have signed the plea, and I’m not sure a significant difference could be established on the basis of this criterion, even if it is an interesting hypothesis to explore.

  25. […] to Terrorism”, European Journal of International Law (EJIL Talk), July 14, 2016, available here […]

  26. […] to Terrorism”, European Journal of International Law (EJIL Talk), July 14, 2016, disponible  aquí […]