Home EJIL Analysis Belgium’s Article 51 Letter to the Security Council [UPDATED]

Belgium’s Article 51 Letter to the Security Council [UPDATED]

Published on June 17, 2016        Author: 

On 7 June, the government of Belgium sent an Article 51 letter to the President of the Security Council, justifying its military action on the territory of Syria against ISIS by way of collective self-defense. The ODS link to the letter is here (S/2016/523), and here is the key paragraph articulating Belgium’s legal position:

ISIL has occupied a certain part of Syrian territory over which the Government of the Syrian Arab Republic does not, at this time, exercise effective control. In the light of this exceptional situation, States that have been subjected to armed attack by ISIL originating in that part of the Syrian territory are therefore justified under Article 51 of the Charter to take necessary measures of self-defence. Exercising the right of collective self-defence, Belgium will support the military measures of those States that have been subjected to attacks by ISIL. Those measures are directed against the so-called “Islamic State in Iraq and the Levant” and not against the Syrian Arab Republic.

Interestingly, this paragraph is taken almost word-for-word from the letter Germany had sent to the Council on 10 December 2015, S/2015/946:

ISIL has occupied a certain part of Syrian territory over which the Government of the Syrian Arab Republic does not at this time exercise effective control. States that have been subjected to armed attack by ISIL originating in this part of Syrian territory, are therefore justified under Article 51 of the Charter of the United Nations to take necessary measures of self-defence, even without the consent of the Government of the Syrian Arab Republic. Exercising the right of collective self-defence, Germany will now support the military measures of those States that have been subjected to attacks by ISIL.

Note, however, some of the differences: Belgium calls this an exceptional situation, somewhat diplomatically removes the reference to the lack of any need for Syria’s consent, even though that’s implicit in its invocation of Article 51, and adds a sentence saying that measures taken in self-defence are directed at ISIS rather than against Syria (even if Belgian airplanes are flying in Syrian airspace and discharging weaponry on Syrian territory without its consent). Both Germany and Belgium endorse a position whereby action against a non-state actor operating from the territory of another state is permitted without that state’s consent if the state lost effective control over the relevant area – this is very close to, but not necessarily exactly the same thing, as the ‘unwilling and unable’ test.

UPDATE: Many thanks to everyone contributing in the comments. I’d say that perhaps the most valuable lesson to be learned from this discussion is how all of these states are strategically using ambiguity in their various letters to the Council. They know perfectly well that the formulations that they have chosen are open to several possible interpretations, and they were deliberately chosen precisely with that in mind – not simply as a matter of diplomacy, but in order to create legal cover for what they want to do today while keeping their options open for the future. Nothing less could be expected, of course, when we bear in mind that the Council’s ISIS resolution 2249 is itself a masterful example of such a use of ambiguity. But ambiguity of this kind is also obviously detrimental when it comes to solidifying a clear position with regard to self-defence against non-state actors on the basis of state (and UNSC) practice.

In that regard, a kind reader also let me know that Norway has also sent a letter to the Council, dated 3 June, S/2016/513. The three key paragraphs are quoted below the fold – note how simply wonderful Norway is in saying nothing, beyond simply stating that it is exercising the right to collective self-defence without directing its actions against Syria.

I am writing in accordance with Article 51 of the Charter of the United Nations to report to the Security Council that the Government of Norway is taking necessary and proportionate measures against the terrorist organization Islamic State in Iraq and the Levant (ISIL, also known as Da’esh) in Syria in the exercise of the right of collective self-defence.

The Security Council recognized in its resolution 2249 (2015) that ISIL constituted a global and unprecedented threat to international peace and security and called upon Member States to prevent and suppress terrorist acts committed by ISIL and to eradicate the safe haven that ISIL had established over significant parts of Iraq and Syria. The Council reiterated that call in its resolution 2254 (2015). In that respect, the Council noted the letters dated 25 June 2014 (S/2014/440) and 20 September 2014 (S/2014/691) from the Iraqi authorities stating that ISIL had established a safe haven outside Iraqi borders in Syria that was a direct threat to the security of the Iraqi people and territory. The Government of Iraq requested the United States to lead international efforts to strike ISIL sites and military strongholds.

Pursuant to that request, the Government of Norway is taking measures against ISIL in accordance with Article 51 of the Charter of the United Nations. The measures are directed against ISIL, not against the Arab Republic of Syria.

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37 Responses

  1. Jasmin Johurun Nessa (PhD Candidate from the Univeristy of Liverpool)

    I agree with your interpretation that both Germany and Belgium appear to be alluding to something similar to the ‘unable and unwilling’ test.
    Perhaps another interpretation for the specific choice of words adopted in both letters suggest that the deliberate reference to ‘effective control’ indicates that Germany and Belgium clearly recognise that Daesh are not attributed to Syria (under the ICJ standard of ‘effective control’). Yet, despite this lack of attribution to a state, both Germany and Belgium still believe that self-defence pursuant to Article 51 can be invoked against a stand-alone non-state actor. If this is the case, then this would be an incredible departure from the ICJ jurisprudence on self-defence and non-state actors.
    Just wondering what your thoughts would be on this?

  2. In my view both Germany’s and Belgium’s notification letter has to be seen as evidence of their discomfort with the “unwilling or unable” test. They are intended to foster an alternative line of argument going more into the direction of the idea of “ungoverned space”.

  3. Marko Milanovic Marko Milanovic


    I’m not sure that inference can be drawn so clearly. In particular, the ‘effective control’ referred to by the two states is NOT an attribution test a la Nicaruaga/Bosnian Genocide, since that test relates to the control exercised by a state over a non-state actor, whereas the control mentioned here is control over territory. But I would say that it does seem likely that Germany and Belgium endorse a theory of self-defence that does not require the armed attack by a NSA to be attributed to a state, at least in those situations in which the attack emanates from a territory not controlled by the relevant state.


    I agree that is a possible interpretation – but the statements are ambiguous enough that they could be interpreted the other way as well. In other words, they clearly address one potential situation of the territorial state’s inability to prevent the attacks of a NSA against another state, but they are silent on other possible scenarios. I don’t think we can clearly infer from that silence that Germany and Belgium think that self-defence arises ONLY in the scenario which they do address, and not in others (e.g. unwillingness or other forms of inability).

  4. Dapo Akande Dapo Akande


    As Marko says I don’t think the statement of Germany and Belgium can necessarily be read as discomfort with the so called “unwilling or unable” test. In fact I would say it is hard to read their statements as being anything other than supportive of the so called “unwilling or unable” requirement.

    It is useful to recall that the so called “unwilling or unable” test is not a self-standing requirement. It is simply an expression of the view that where the territorial state is either unwilling or unable to take action against the non-state group based on its territory, it will (personally I would say “may”) be necessary for the attacked state to use force. So it is merely an application of the necessity requirement for lawful acts of self defence.

    Germany and Belgium’s reference to loss of effective control of territory is also linked to the necessity requirement. What Germany and Belgium seem to be saying that is that because Syria does not have effective control of the territory then it is necessary for them to use force in self defence. But why would loss of control of territory be relevant here? Well, I would have thought it is only relevant because it indicates that Syria is unable to take action against ISIL.

    The line of argument I have just spelled out is implied in the links between the first and second sentences quoted by Marko. The argument made in the second sentence about “necessary measures of self-defence” is made “in the light of” the loss of effective control point referred to in the first sentence. Note also that in the light of ISILs control of territory and Syria’s lack of control, states subject to armed attacks by ISIL are therefore justified in taking necessary measures of self defence. So the first sentence sets out the grounds on which a necessity claim is made in the second sentence. This necessity claim is based on the inability of Syria to take action.

    Having said that Germany and Belgium are relying on a type of “unable” argument, it is not clear whether the only circumstance which in their view would make a state unable to act is when it has lost effective control of territory. To focus on this though is to lose sight of the broader points that (i) they are making an argument based on the same logic as the unwilling or unable interpretation of necessity and (ii) the factual circumstance they are dealing with is one of loss of territory, but that this is only relevant because it leads to inability of the territorial state to take action.

  5. Michael G. Karnavas

    A slippery slope however you slice and dice this argument for intervention. But then who will actually do anything about this action if in fact it is unlawful.

  6. Raphael Van Steenberghe Raphaël van Steenberghe

    Just three comments :

    – First, the Belgian letter is slightly different from the German one as it refers to an “exceptional situation” in its justification (third paragraph). Those terms are ambiguous. Do they refer only (as I think) to the situation of lack of control by the Syrian government, as just mentioned before, or to the situation of Daech in general? In the latter case, this would mean that Belgium has made an exceptional interpretation of the law of self-defence (derogating from the classical one) because of the exceptional situation. One could not therefore infer from the letter that Belgium’s opinion is that self-defence can always be invoked in response to armed attacks by non-State actors when the attacks come from a territory not controlled by the State where those actors are located. This is an interesting issue. We know that arguments based on the exceptional nature of the situation have already been invoked to justify exceptional derogation to the law on use of force (cf. intervention in Kosovo in 1999). More particularly, a French legal advisor has recently written in an international law journal that departure by France from the classical interpretation of the law of self-defence (according to which armed attack must come from a State) was due to the exceptional nature of Daech – the French authorities did not however officially invoke such “exceptionalism” to justify this departure.

    – Second, regarding the unwilling or unable test: I share Dapo’s view. The Belgium’s formulation is another way to express the requirement stemming from such a test (itself deriving from the general condition of necessity) in case of actions in self-defence in response to armed attacks by non-State actors. Moreover, one should keep in mind that German official documents expressly refer to the test – that Germany therefore seems to endorse ( There is no such document in Belgium. There were some discussions before the Parliament (, where the Minister for Foreign Affairs said that “it is on the basis of Article 51 (of the UN Charter) and at the request of the Iraqi government in terms of defence and self-defence against attacks from Daech, located in a part of the Syrian territory over which the government has no control, that we intervene” (my translation). Records of a second round of discussions held before the Parliament on the adoption of a resolution supporting the intervention will be available soon (probably next week).

    – Third, although the letter starts by mentioning that Belgium will exercise collective self-defence at the request of Iraq (argument also made by the Belgian Prime Minister before the Parliament), the third paragraph suggests that Belgium will also exercise collective self-defence for the protection of other States which have been victim of attacks by Daech (maybe France – note that France is expressly mentioned in the German letter). This ambiguity was probably deliberate. This allows Belgium to avoid pronouncing on the qualification of some terrorist attacks (like in Paris) as armed attack under Art. 51. It is also interesting to note in that regard that (contrary to France) Belgium did not invoke individual self-defence although it has been the object of attacks by Daech on 22 March.

  7. Dear Marko and Dapo,

    You’re probably right that, in the letters, loss of effective control over territory simply helps explain the necessity to use defensive force. Let me throw out two other possibilities, in case others find them interesting.

    First, in the Belgium letter, Syria’s loss of territorial control may support the claim that force is ‘directed against’ Daesh and ‘not against’ Syria. I doubt it (if force was truly not directed ‘against’ Syria, would Belgium even need to invoke self-defense?) but it’s possible.

    Second, in the Germany letter, Syria’s loss of territorial control may support the claim that force is justified ‘even without the consent of the Government of the Syrian Arab Republic’. When State A attacks State B, State A obviously forfeits its right not to have force used on its territory without its consent. In contrast, when an independent armed group launches an armed attack from the territory of State T, what happens to State T’s right not to have force used on its territory without its consent? One possibility is that State T’s right may be overridden by the exceptional gravity of the armed attacks launched from its territory. Another possibility is that State T’s right is involuntarily lost when it loses effective control over the part of its territory from which the attacks emanate. Perhaps the Germany letter means to claim the latter with respect to Syria. Again, I doubt it, but it’s possible.

    Just some food for thought. Thanks very much for the post, and for the comments.

    Very best,


  8. Jasmin Johurun Nessa

    Thank you for the clarification, Marco! Very helpful.

    Its difficult not to draw the connection when, clearly, Syria does not have effective control over it’s territory because it does not have effective control over the non-state actor on its territory.

  9. Yes, thanks for this post. My first impression was quite different. My sense was that the Belgium/Germany approach was quite different from “unwilling/unable” in that it endorsed “unable” but not “unwilling”. And even with regard to unable, the Belgium/Germany approach requires more than simply a terrorist organisation with so much clout in the country that they are untouchable, it requires that the organisation has prevented the state from excercising effective control over part of the country (or that it has otherwise taken advantage of a lack of effective control).

    This means, for example, that the Belgium/Germany approach could never work against Hezbollah in Lebanon. Under unwilling/unable you could easily imagine a situation where the Lebanese government is unwilling and/or unable – depending on your perspective, and on who you count as part of the Lebanese government – to prevent Hezbollah from using Lebanon as a basis for attacks in Syria. But under the Belgium/Germany approach you could never attack Lebanon in response, because the Lebanese government excercises effective control over all of its territory (as far as I understand).

  10. Dapo Akande Dapo Akande


    I agree that these are possibilities but also agree that they are not plausible arguments. As you suggest (1) would be based on the view that there is not even a prima facie violation of art. 2(4) vis a vis Syria but if that were so there would be no need to rely on self defence under Art. 51 (and therefore no need for the letter). To the extent that (2) is not based on an invocation of self defence with respect to Syria, it would seem to me to be just a variant of 1.

  11. In my view, the Belgian position is highly ambiguous.
    However, in my opinion, by stating (like Germany did) that the (future) bombing of the Syrian territory wouldn’t be directed ‘against the Syrian Arab Republic’, the Belgian position is simply absurd. “Every State has the duty to refrain from the threat or use of force to violate the existing international boundaries of another State” (GA res 2615); “[a clear exemple of aggression is the] Bombardment by the armed forces of a State against the territory of another State or the use of any weapons by a State against the territory of another State;’ (GA res 3314). By bombing the Syrian territory, by destroying Syrian buildings and facilities, and by killing or wounding Syrian citizens, Belgium will obviously use of force against Syria (and not only against ISIL). Of course, a use of force can be justified by self-defence, but this would require to invoke it vis-à-vis the victim of the use of force, i.e. the Syrian State. This is probably why the US (but also Australia and Canada, even if those two States first refused to follow the US arguments ) accused Syria of being ‘unwilling and unable’ to combat ISIL (which is rather curious,if we know that the Syrian authorities are at least able to consent to a foreign military intervention, and that they did it, which show that they are ‘willing’ to put an en to the ISIL activities). By contrast, when they stress the ‘exceptionality’ of the situation, the Belgian authorities show they reluctance to establish a precedent (I share Raphael’s suggestion in this regard). In this regard (but also by comparing the letters sent to the SC respectively by the US and by Belgium), to argue that Belgium used the same legal line of reasoning that the US is not very convincing (I share Paulina’s view). Actually, and this is very clear not only by comparing the letters but also by consulting the parliamentary debates, the Belgians preferred to follow their European colleagues. It this regard, it is interesting to note that the French clearly expressed they refusal to endorse the unwilling or unable argument (see the developments made by François Alabrune, directeur des affaires juridiques of the French Minister of Foreign Affairs in Revue générale de droit international public, 2016). A final word: legally speaking, even for those who consider that the necessity criterion would be the only relevant to assess the validity of a self-defence argument, how to justify that the consent of the Syrian authorities has not been (at least) asked? Well, what is sure is that the Belgian letter (no more than the others referring to self-defence) does not give any answer to that…

  12. Marko Milanovic Marko Milanovic

    Thanks to everyone for the comments. I particularly agree with Olivier’s point about the ambiguity of the whole thing. I just updated the post with some further thoughts and a reference to another very recent letter to the Council, this time by Norway.

  13. Doug Cantwell

    Great post and interesting discussion. A few months back, U.S. State Department Legal Adviser Brian Egan gave a keynote speech at ASIL in which he suggested that loss of effective control gave the U.S. grounds to use force against ISIS in Syria under the “unable” prong of the “unwilling or unable” test. In Egan’s words:

    “With respect to the “unable” prong of the standard, inability perhaps can be demonstrated most plainly, for example, where a State has lost or abandoned effective control over the portion of its territory from which the non-State actor is operating. This is the case with respect to the situation in Syria. By September 2014, the Syrian government had lost effective control of much of eastern and northeastern Syria, with much of that territory under ISIL’s control.”

    This challenges Marko’s conclusion in the post that Belgium and Germany’s position “is very close to, but not necessarily exactly the same thing, as the ‘unwilling and unable’ test.” (At least as the test seems to be understood by the U.S. government).

    I go into more detail in a blog post on why Egan’s invocation of effective control, as one potential factor in an otherwise ambiguous test for inability, may be troubling from the perspective of international law:

    Interestingly, the Article 51 letter that the U.S. submitted to the UNSG in September 2014 does not contain an explicit mention of loss of effective control. (In that sense, Norway’s letter more closely resembles the U.S. letter than the German/Belgian formulation). In fact, from what I have been able to find, the Secretary General’s response to that letter was the first mention of the Assad regime’s lost of effective control. SG Ban said:

    “I am aware that today’s strikes were not carried out at the direct request of the Syrian Government, but I note that the Government was informed beforehand. I also note that the strikes took place in areas no longer under the effective control of that Government. I think it is undeniable – and the subject of broad international consensus – that these extremist groups pose an immediate threat to international peace and security.”

    Would be interested in hearing any thoughts on why the SG mentioned effective control at that time, where this loss of effective control theory may have originated before it was picked up by the SG, and how it has shaped the debate since, including in subsequent Article 51 letters.

  14. What an excellent blog post!

    We should keep in mind that the “effective control” scheme is reminiscent of Art. 42 of the Regulations annexed to the Hague Conventions (II/1899, IV/1907) respecting the laws & customs of war on land. It has been pointed out that the effective control argument bears little resemblance to the Nicaragua and/or Bosnian Genocide dictum; that’s a truism. Actually, the effective control criterion as called upon in the present case, one might argue, has nothing to do with jus ad bellum at all.
    To elaborate: Even if the scheme is utilized in order to justify and mobilize the collective security mechanisms as provided by the law of self-help (collective self-defence, Art. 51 of the UN Charter) [jus ad bellum], it ontologically and functionally pertains to the jus in bello.
    The “effective control” criterion, as used by the Art. 51 Letters under scrutiny in the present post, is a precondition sine qua non [cf Y Dinstein, The Intl L of Belligerent Occupation (CUP, 2009) 43ff] for the overall application of the law of belligerent occupation. Regardless of its status as a non-state actor, ISIL/Daesh can be considered occupying power under both the traditional doctrine of the Hostages Case (longa manu occupation, effective overall control) and the Naletilić doctrine (pragmatic control) [ICTY, Case No IT-98-34-T, Prosecutor v Mladen Naletilić (2003), para 217].
    Furthermore, since the micro-constitution of the law of belligerent occupation (Art. 42 of the Hague 1899/1907 Regulations) possesses both conventional and customary status [Cession of Vessels and Tugs for Navigation on the Danube, ad hoc Arbitral Award of 2 August 1921; Lighthouses Case between France and Greece, [1934] PCIJ Rep Ser A/B No 62, Sep Opinion of Seferiades J; IMT/Nuremberg, USA et al v Göring et al; IMT Far East/Tokyo, Re Hirota et al; ICJ, Wall advisory opinion etc] one may argue that it is applicable vis-à-vis either States and/or non-state actors.
    Such being the case, Daesh can actually be targeted under the jus in bello so as to terminate the occupation, abolish its “precarious and temporary actual control” (US NMT, The Einsatzgruppen Case, 1948) and re-enforce the weakened or naked (Schwarzenberger, 1960, in 30 Nordisk Tidsskrift 10, 17) Syrian sovereignty over the occupied territory by effectively contesting ISIL’s armed force (cf. TMP de Dijon, Carl Franz Bauer et autres, 1949 LRTWC 15, 18).
    Such an approach begs yet another question: Why calling upon a scheme pertaining to the jus in bello (law of belligerent occupation) in order to justify recourse the jus ad bellum (self-defence).
    The gradual blurring of spatial and normative limits between both sections of the international law of the use of force can’t and must not escape our attention (see for instance the self-defence targeting of terrorist actors overseas doctrine, applied by the Obama Administration, during since 2011/2012).
    Powers able and willing to cease the occupation and assist restoring the title of the true sovereign against the occupant are bound to find a way through legal reasoning to justify their recourse to force. The said Powers may even target the sovereign’s facilities and structures in the occupied zone, without its consent, if such actions would ultimately lead to the full restoration of sovereignty in the occupied territory (proportionality analysis), since the status of belligerent occupation and the ongoing conflict have rendered the occupied zone hostile territory for both the true sovereign and the assisting Powers. The aforementioned Powers can mobilize Art. 51 mechanisms to trigger a permissive title for the utilization of armed force and Art. 42 (Hague Regulations) criteria so as to delimit their operational field.
    PS Given the state of international affairs created under S/RES/2249, I need to point out that the ideas expressed in the present comment are both rudimentary and open to objections-observations etc. Finally, allow me once more to congratulate both the author and the other contributors for their most interesting comments in the present debate.

  15. Marty Lederman

    I agree with virtually all of what Dapo and Marko have written, except that (contra Marko) I don’t see anything at all “ambiguous” in the Belgium/Germany/Sweden letters. They are all asserting — as many other nations have done — that an “armed attack” for purposes of Article 51 can consist of an attack by a nonstate organization, even if that attack is no meaningful way “attributable” to the host state.

    That view is hardly an “incredible departure” from established international law, let alone a “derogation” from the “classical” view. Indeed, it describes the Caroline case itself (which I had thought was the canonical source of the “classical” position!); many states have acted in accord with it, both before and after the Charter; many states have now expressly endorsed it; and, as far as I know, virtually *no* states (as opposed to publicists) have rejected it. (I don’t think it’s even inconsistent with the ICJ decisions, but that’s a longer story.)

    I don’t read the Belgian statement to be suggesting an “exceptional” *departure* from the law, but instead merely to be noting that such a use of force against a NSA without host-state consent will only be “necessary” — and thus lawful — in rare cases.

    I think Dapo is right that “unable or unwilling” is simply an application of the requirement of “necessity” in cases where the NSA has taken refuge in a nonconsenting state. I also agree that there’s no hint in these statements of any doubts about the legality of striking the nonstate actor in a different case–not presented here–in which the host state has effective control, and thus could do something to prevent the NSA’s attacks, but declines (is “unwilling”) to do so. Why *shouldn’t* the threatened state be able to target the NSA in such a case?

    I also think that the Belgian and Swedish clarifications that the measures are “directed at” ISIL rather than Syria are very welcome and helpful (not least in distinguishing this case from, e.g. the Nicaragua case). I, for one, did not understand those statements to be assertions that the use of force is not “against the territorial integrity” of the state for purposes of Art. 2(4)–I agree with Prof. Corten that such a view would be “absurd”; instead, they are simply acknowledging another limitation on the Article 51 exception–namely, that the action in self-defense must be proportionate to the threat, as well as necessary: An attack on Syrian forces or officials or resources or civilians, as such, would not be sufficiently tailored to stopping the threat from ISIL, and therefore would not be lawful.

  16. But the question remains: how can you justify a use of force against a State without establishing a right to self-defence against this State? The problem is not to show that self-defence can be used against NSA. The argument is useless, as there is simply no prohibition to use force against them (article 2.4 only govern ‘international relations’, i.e. relations between States), and if there is no prohibition, there is no need to invoke any exception (like self-defence) to this prohibition. By contrast, self-defence must come into play when a State uses force against another State (here Syria). This is why the US (and later Australia, Canada and Turkey – which was by the way strongly condemned by several States) accused Syria of being ‘unwilling or unable’ to put an end to ISIL activities. The European States intentionally (see the details of the French position) chose another line of reasoning, by contending that their use of force was not “directed against the Republic of Syria”, which is different (even if it isn’t clearly expressed at all, as our discussion confirm). At this stage, it is difficult to understand how the bombing of the territory, the destroying of public goods and the killing or wounding of nationals (civilians or not, ‘as such’ or not) could be considered as ‘not directed against’ the State… These difficulties explain probably why (and here again a reading of the French position in RGDIP 2016 is useful) some European States evoked the ‘exceptionality’ of the situation. Finally, I’d like to stress that necessity and proportionality, in contemporary international law (i.e. deduced from the Charter system, and not from IL as it existed in 1837 or in 1899), are NOT conceived as legal titles allowing States to intervene militarily wherever they want; on the contrary, those criteria are rather restricting the possibilities to use force (see the ILC works or the ICJ case-law, among others). And, even if you conceive necessity as a title, I repeat my question: how can you justify that the consent of the Syrian authorities has not been (at least) asked in this particular case?

  17. Hi Olivier,

    I’ve enjoyed your comments, and thought I’d underscore two of your points.

    I agree that what must be justified is not the use of force against an independent non-state actor as such but rather the use of force against (on the territory of) the territorial state. The view that ordinary criteria of armed attack, necessity, and proportionality suffice to justify the latter seems hard to accept. If states have a right not to have force used on their territory then generally that right must be either waived (through consent) or forfeited (through responsibility for an armed attack).

    In particular, it seems hard to believe that using force on the territory of a state that *is* responsible for an armed attack is legally equivalent to (subject to the same legal criteria as) using force on the territory of a state that *is not* responsible for an armed attack. That seems tantamount to denying the existence of the right itself.

    However, I am open to the possibility that a state’s right not to have force used on its territory may be overridden (by the exceptional gravity of an attack by an independent non-state actor) or involuntarily lost (through loss of effective control over territory). I would rather see the law develop in one of those directions than simply adopt the ‘unwilling or unable’ standard.

    I also agree that, if applicable in such cases, necessity would require the exhaustion of reasonable alternatives to *non-consensual* force. As you suggest, the necessity to use force does not entail the necessity to use force without consent.

    Best wishes,


  18. Marty Lederman

    Adil (and Prof. Corten): Agreed: Using force on the territory of a state that *is* responsible for a non-state actor’s armed attack is not “legally equivalent to (subject to the same legal criteria as)” using force on the territory of a state that *is not* responsible for that NSA’s armed attack — in particular, the type of force that is proportionate to the threat, and thus that may properly be used, differs in the two cases: As the Belgian letter indicates, in the latter case it would not be proportionate to direct force against the host state’s military, or military objects, as such, whereas in the former case — say, for instance, where the host state’s military is defending the NSA — such an expanded use of force might be proportionate to the threat.

    Even so, what *triggers* the Article 51 “inherent right” to use force in self-defense against the territorial integrity of the state (again, assuming the requirements of necessity and proportionality are satisfied) is the existence and threat of an armed attack emanating from that state, regardless of whether the attack is committed by the state itself or by a private organization that has taken refuge there, and regardless of whether the state is in some strong sense responsible for the attack. The language and logic of Article 51 do not impose any precondition that the host state have committed, or be responsible for, the armed attack. And that makes sense. For one thing, it describes precisely what occurred in the Caroline case (the rebel attacks were in no way “attributable” to the U.S.), and that case presumably is an important historical precedent for understanding the “inherent” right of self-defense. Moreover, it’s simply implausible to think that any of the states signing the Charter–let alone most or all of them–would have intended to deny themselves the ability to address such an NSA attack under Caroline-like circumstances — which is why both state practice and the virtually unbroken public views of states in recent decades support the U.S./France/U.K./Belgian/Noweigian/etc. reading of Article 51.

  19. Hi Marty,

    Good to hear from you, as always. You write that “The language and logic of Article 51 do not impose any precondition that the host state have committed, or be responsible for, the armed attack.” Naturally, I disagree.

    Article 51 recognizes a right of *self-defense*, not a right of self-preservation. Self-defense justifies harming those who pose a threat or who are responsible for a threat, and who thereby make themselves liable to defensive force. If defensive force also harms others, *not* responsible for a threat and who have *not* made themselves liable to defensive force, then that additional harm requires some other form of justification: waiver (consent), override (lesser evils), etc.

    At some personal risk, let me try to illustrate the point with an unrealistic hypothetical: Suppose that Marko unlawfully attacks Dapo. Since Marko is responsible for the threat that he poses to Dapo, Marko is liable to necessary and proportionate defensive force. Now suppose that, if Dapo uses defensive force against Marko, he will also harm Olivier, an entirely innocent bystander. Clearly, Dapo cannot claim self-defense with respect to Olivier. Accordingly, Dapo would have to justify the “collateral” harm to Olivier on some other grounds (consent, lesser evils, etc).

    Similarly, if the territorial state is not responsible for the threat posed by the non-state actor then the territorial state has done nothing unlawful or wrongful to make itself liable to defensive force. The use of defensive force on its territory, and the resulting harm, therefore requires some other form of justification (consent, exceptional gravity of the threat, etc), and cannot rest on self-defense alone.

    You also write that “it’s simply implausible to think that any of the states signing the Charter–let alone most or all of them–would have intended to deny themselves the ability to address such an NSA attack under Caroline-like circumstances.” Perhaps. Still, I wonder: is it more plausible to think that all or most states signing the Charter intended to permit the use of force on their territory without their consent and without any unlawful action or wrongful conduct on their part?

    Hope all is well,


  20. Marty Lederman

    Adil: Thanks for the characteristically thoughtful response. I think our principal difference is that I don’t see any reason to treat Article 51 as a “liability” provision at all. The basis for allowing a use of force that violates the territorial integrity of a state is not to punish that state, but instead simply to defend the acting state from armed attacks emanating from that state. Indeed, even if the host state *has* done something wrong–something that clearly warrants punishment, or reparations–that would not justify an act of self-defense under Article 51 if there is no threat of further attack. Pure, or punitive, reprisals are not permitted. That’s simply not the office of Article 51.

    To use an analogy from domestic law, derived from your hypo: Say Olivier is a landowner. The law of trespass generally protects the “territorial integrity” of his land against invasion (and, or course, against destruction). But let’s say a particularly vicious squatter–Marko–takes up residence on that land, and from there launches attacks, or creates nuisances, that harm Dapo, someone living outside the land. For some reason Olivier can’t (or won’t) stop Marko from causing the harm (perhaps Marko has terrorized Olivier as well, for instance). Surely, Dapo — or the police, at least — can take steps *against Marko* to stop the attacks/nuisance, even if those steps will intrude upon the integrity of Olivier’s land, an integrity that the law otherwise protects.

    But, you ask: What about the collateral harm to Olivier’s land? How can that be justified, since Olivier didn’t do anything wrongful? Well, such harm can’t be justified if it’s gratuitous–and perhaps not even if it is excessive in relation to the amelioration of the threat to Dapo from Marko. And, surely, it is *not* ok for Dapo to target Olivier himself, or other property of his that is unrelated to the Marko threat. (That’s the thrust of Belgium’s statement that it is not targeting Syria as such.) Requirements of proportionality are designed to deal with precisely such concerns. But just as there is no absolute bar to any and all collateral damage to innocent Olivier in my hypothetical, so, too, the jus ad bellum does not categorically prohibit all harm to non-liable states (just as the jus in bello does not guarantee that no civilians will be killed). (Once again: The burning of the Caroline was accomplished via a violation of the “territorial integrity” of the U.S. — but no one, least of all Daniel Webster, thought that that violation of integrity, in and of itself, rendered unlawful the British act of self-defense. The difference between the two sides was, well, whether the U.S. was in fact unable to prevent future rebel attacks.)

  21. Federica Paddeu

    Interesting discussion, as ever.

    On Adil and Marty’s arguments (if I can use your first names), I think a little Hohfeld might help clarify a few things. Your arguments are not, in fact, all that different: it’s simply that Adil is arguing from the standpoint of the State who suffers force in its territory and Marty from the standpoint of the State who uses force. But as Hohfeld explains, neither of these positions can stand on their own: one does not have a ‘right'(or a liberty, or a power, or an immunity) in a vacuum. These are always asserted in the context of a legal relation: as against someone else. For example, to say that A has a (claim-)right to do something is the same thing as saying that B has a duty not to interfere with A doing that something. So, to say that a State has a ‘right’ (I am using inverted commas here, so as not to prejudge what kind of entitlement self-defence actually is) of self-defence is also to assert that someone else will be in a given relation with respect to that exercise of self-defence. If we use Hohfelfd’s first-order legal relations, self-defence can be seen as a liberty (or privilege) of a State, in which case another State will have a (correlative) no-right that self-defence not be used against it. Equally (to use the second-order legal relations) self-defence can be seen as a power of a State, in which case another State will have a liability in respect of the exercise of that power.

    Now, these are always A-B relations with respect to a given thing X. The moment an additional party is added (say C), then the relations between A-C and B-C have to be analysed separately. And here I think Adil is right: the self-defence relation (eg, the relation of Article 51) exists between the State (A) and the Non State-Actor (B). The host State (C) is a third party in that relation, and so the no-right or the liability of the host State to the forcible action of the State exercising self-defence must be explained in some way other than by reference to Article 51. I think Article 21 of the Articles on State Responsibility can provide the additional justification necessary in this regard (in the A-C relation)–but I acknowledge that there is no practice backing this explanation.

    Separate from this analytical explanation, is the theoretical explanation (or even the moral explanation) for the legality of self-defence. In this regard, forfeiture theory is a common way to explain the legality of self-defensive force among criminal law theorists and moral philosophers (see, eg, Uniacke, Permissible Killing (1994); Fletcher & Ohlin, Defending Humanity (2013)). This theoretical explanation can incorporate Hohfeldian analysis, in that it can be broken down into the victim possessing a liberty to interfere with the aggressor’s life and the aggressor having a no-right that his life be respected by the victim (the aggressor’s no-right would be the result of his having forfeited that right by his aggression). This is not, however, generally accepted nor pacific as a moral explanation of the legality of self-defence–at least in respect of the right to life (see, eg, McMahan, Killing in War (2009). The objections to this theory in criminal law stem mostly from the moral value of life and how it cannot renounced/forfeited. But these moral objections are less valid when talking about States, so rights-forfeiture provides a persuasive explanation for the legality of self-defence in international law (of course, in the A-B relations between victim and aggressor).

  22. Thanks Federica, for that erudite intervention, which I quite enjoyed. Did you mean to type Article 21 (self-defense) or Article 25 (necessity)?

    Marty, in your hypothetical, harm to Marko may be justified as self-defense, but harm to Olivier’s property could only be justified as a lesser evil. Marko has lost his right against defensive harm, while Olivier’s right against harm to his property is retained but may be outweighed or overridden to prevent significantly greater harm to Dapo.

    Similarly, assuming that self-defense under Article 51 justifies harm to independent non-state actors, the infringement of the territorial state’s rights may be justifiable as a lesser evil. The territorial state has done nothing to lose its rights, but its rights may be outweighed or overridden to prevent significantly greater harm to the intervening state.

    As you observe, there is an interpretation of jus ad bellum proportionality that weighs the harm prevented by defensive force against the harm inflicted by defensive force. On this interpretation, the infringement of the right of the territorial state could simply be one factor in the proportionality analysis. Indeed, this is the interpretation of jus ad bellum proportionality that I favor. Unfortunately, this interpretation is rejected by most international lawyers. The majority view is that jus ad bellum proportionality requires only that defensive force inflict no more harm than necessary to achieve its defensive aim, even if the former clearly outweighs the latter from an impartial point of view.

    How, then, to recognize the rights of the territorial state through a “lesser evils” analysis? As I think Federica meant to type, one possibility would be to expand the scope of necessity under Article 25 of the Articles on State Responsibility. I’m open to that option, although others disagree.

    Importantly, in my view, the infringement of the right of the territorial state would be a lesser evil (or proportionate on the minority interpretation we favor) only if the non-state actor launches an attack of exceptional gravity, significantly exceeding the ordinary “armed attack” threshold. The reason for this is that a use of force that barely meets the “armed attack” threshold is barely sufficient to justify harming a state that is responsible for that armed attack. Certainly, such a use of force cannot be sufficient to justify harming a state that is not responsible for that armed attack.

    Very best,


  23. Very interesting discussion but, just to be clear, Marko didn’t terrorize me!. More seriously, this analogy with municipal law can be instructive. In the situation Marty imagines (at least in all the domestic legal systems I know), Dapo couldn’t simply enter and destroy my property in the name of its self-defence against Marko. Actually, he should ask me to enter my property to have some discussion with Marko or, if I don’t want or I’m not able to do so, to call the police to address the problem. If we transpose it to international law, Belgium is supposed to ask Syria to consent to its military operations or, if Syria is unwilling to do so (and I repeat once again, Syria, being a State and having a government, is by definition able to consent to a foreign military operation- this is why the ‘inability’ criterion is simply not relevant), to require the Security Council to do so. It is only in the hypothesis the SC does not take necessary measures that self-defence could be invoked, at least if the ‘unwillingness’ of Syria could be considered as equivalent to an ‘armed attack’ (by using the ‘substantial involvement’ condition laid down in art3g) of the definition of aggression). Against this background, it must me stressed that State C (in Federica’s hypothesis) – Syria, in other words— is NOT a ‘third’ party. I guess we agree that the State cannot be reduced to its government. If you bomb the territory of a State, the population of a State (and incidentally the public goods of this State), you use force against this State, and the State attacked can obviously invoke Article 2.4 against you. In other words, if Belgium bombs Syria, it will attack Syria ‘as such’. Finally, and more generally, I’m always puzzled by those who stress the necessity for international law to be adapted to the evolutions of international relations, and in the same breath seem to consider that a letter written in 1837 should be considering as governing IL of the 21st century. Methodologically speaking, I strongly believe the correct way to proceed is to start by establishing the original meaning of the text (here the UN Charter): and it is obvious that the UN Member States initially conceived jus contra bellum as a regime governing the relations between States. Of course, a new interpretation of the Charter can emerge, and we can all give our opinion about what would be the ‘ideal’ new rules governing the use of force when a NSA is implied. However, the problem, in positive international law, is that this new interpretation should be eventually accepted by the ‘international community of States as a whole’ (not by a limited number of -mostly Western— authors or States). And, as far as I know, the vast majority of States remain reluctant to accept such a change, as reveals for example this statement made by the Non-Aligned Movement (more than 110 States) made in 2014: ‘… 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;’ (NAM, Algiers, Algeria 26-29 May 2014, Final Document, A/68/966–S/2014/573, 19 August 2014).

  24. Hi again Marty,

    Apologies, I forgot to respond to your opening paragraph. As Federica indicates, “liability to X” simply means “no right against X”, not “deserving of X”. So I entirely agree that the aim of defensive force is not to punish past wrongdoing but rather to prevent an unjust threat from materializing.

    However, only those responsible for an unjust threat are liable to (have lost their right against) harm inflicted in self-defense. All others retain their rights not to be harmed. Accordingly, harm to such innocent third parties must be justified on some other grounds (consent, lesser evils, etc). I hope that clarifies things a bit.

    Very best,


  25. Federica Paddeu

    Hi Adil,

    I did mean Article 21 (as self-defence), and not Article 25 (state of necessity). The lesser-evils argument can of course be made but the difficulty with it is that it is not generally accepted that state of necessity can be relied upon to justify the use of force (mind you, self-defence can also be theoretically explained on consequentialist theories such as lesser evils). Article 21, instead, is intended to justify the breach of ‘other’ obligations caused by the use of force — the collateral violations that were mentioned earlier. In particular, the Commentary to Article 21 does not exclude that self-defence as a justification might operate as against a third State (para 5 of the Commentary), whose rights and other legally protected interests may be infringed by the lawful exercise of self-defence. (I have written about this in a forthcoming LJIL article, which you can access here: Apologies for the self-promotion, those who know me will also know this is rather out-of-character! But I think it may be useful to explain what I mean further).

    As to Olivier’s point on third parties, I used the term ‘third’ only to make the Hohfeldian analysis. In the sense that if the self-defence relation exists between A-B and it relates specifically to the use of defensive force as between those two parties, then where a non-State actor is involved then the relation exists between the defending State and the non-State actor. So the right of self-defence (Article 51 or its customary equivalent) cannot itself address the effect of that exercise on the host State. With respect to the host State there are separate legal relations: as between itself and the defending State (C-A) and as between itself and the non-State actor (C-B). These relations need to be addressed separately. The term ‘third’ might be misleading, especially given that there exists a certain degree of involvement between B and C. The difficulty I have found is that of rationalising that fact of State involvement into a legal ground of justification. I put forward my argument of Article 21 ARS, just as Adil referred to Article 25 ARS, as a way of doing so.


  26. Hi Federica,

    Interesting! I look forward to reading your paper.

    Many thanks,


  27. Thanks Federica, interesting and stimulating reflexion! However, I’m not sure that self-defence as a circumstance precluding wrongfulness could be used to justify a use of force against a State. This has been excluded by Article 26 of the ILC Articles and, as you righty pointed out, no practice can be found supporting that possibility. In practice, States systematically invoke self-defence according to Article 51. This is logic, by the way, because Article 51 was conceived precisely to be used to justify a use of force against a State. Against a NSA, self-defence is simply useless, as I mentioned earlier: there is simply no prohibition to use force against a NSA in IL. Finally, this could be of some interest for you:

  28. Federica Paddeu

    Hi Olivier, thanks for the reference. I have read it (many times!) but, as it happens, I disagree with the authors’ arguments about Article 21!

    Article 21 does not justify the resort to force as such–this must be done by reference to the jus ad bellum. I agree with you that the jus ad bellum cannot quite address situations where force is used by/against non-State actors (not only does the prohibition of force not protect non-State actors, it also doesn’t bind them and, as a result of this, there can never be an unlawful armed attack necessary to trigger the right of self-defence. This, I think, is something that is often overlooked and yet it is crucial: if the armed attack is not illegal, but merely a factual condition, then defensive force (a fact) can itself meet the requirement of gravity to amount to an armed attack in fact and thus trigger a right of self-defence, and so on ad infinitum. If the principle no self-defence against self-defence must be upheld, then the triggering condition ought to be illegal. Andre de Hoogh’s recent article in LJIL makes this point quite nicely).

    Nevertheless, Article 21 can justify the infringement of other rights by way of forcible conduct (eg, the impairment of territorial integrity, of non-intervention, and so on) which do not amount to jus cogens rules (which should overcome the Art 26 ARS obstacle). If it is accepted (and am with you that it may not be) that self-defence can lawfully be exercised against a non-State actor (and this takes care, so to speak, of the prohibition of force), we still have the problem of explaining why the host State’s rights of territorial sovereignty, non-intervention, etc are not thereby violated. My argument is that Article 21 ARS can provide a useful or plausible theoretical framework to explain why there would be no violation of these rights. Am not saying in practice States use this argument (I think Article 21 is much misunderstood), but simply that this is a tool which may help us find a way of explaining legally why the host State is liable to force being used in its territory. It’s most certainly an argument about the possible further development of the law, rather than an attempt to explain the current (and very messy) practice.


  29. Dapo Akande Dapo Akande

    Many thanks to Olivier, Adil, Marty, Federica and others for a fascinating and very sophisticated discussion. Olivier and Adil are of the view that when a state suffers an attack from a non-state actor based on the territory of another state, the first state may have right of self-defence against the non-state actor but they question whether it can have a right of self-defence against the second state. The operating assumption seems to be that since the second state has done nothing wrong it is not liable to having force used against it. Thus its rights not have force used against it have not been lost. A few points may be made in response to this:

    1) In legal terms this argument seems to proceed from the assumption that the use of force in self defence is a response to wrongful action. So if there is no responsibility for a wrong (because of lack of attribution), how can the state have lost its right not to have force used against it? It seems to me that viewing self defence through the lens of state responsibility (as in viewing it as a response to wrong doing) is the wrong lens to use. As far as international law is concerned self defence is not a legal remedy for implementing responsibility but rather what it says – a means of defending oneself from attack.

    2) We accept that a state is not just the government but includes the territory as well. So as Oliver says, when one state uses force on the territory of another without its consent, it has used force against the state, even when it does not use force against the government. However, there seems to be a reluctance to accept the converse: that when a threat comes from the territory of a state, that threat comes from the state (not in terms of legal responsibility – which would require attribution) such as to explain why self defence is justified against that state.

    3) In legal terms, a state has the right not to have force used against it but that right is subject to the inherent right of self defence under Art. 51 of the Charter. Therefore, if states are of the view that Art. 51 encompasses responses by states to armed attacks conducted by non-state actors based on the territory of another state, that is not just an interpretation of Art. 51 but also necessarily a limitation of the right of the territorial state not to have force used against it.

    4) All the states who invoke self-defence and Art 51 when they use force against a non-state actor on the territory of another state only do so in order to justify what would otherwise be a breach of Art. 2(4). In short they are all accepting that the right not to have force used against a state can be lost in cases of attacks by non-state actors. I accept of course that we can argue about the conditions they set. But the basic position is the more important one, which is the acceptance that Art. 51 can justify a use of force against a state, when the defending state is responding to an armed attack against a non-state actor.

    5) There are indeed many states that have (now) interpreted Art. 51 in the sense described above. Olivier rightly points us to the NAM statement. The problem is that this bit of the statement is vague in wording. Also some of those members of NAM have themselves interpreted Art. 51 as allowing force in self-defence in response to attacks by non-state actors.

    6) One point that deserves attention is whether proportionality in the jus ad bellum means/should mean the same thing when a state uses force against a non-state actor on the territory of another state. I am one of those who takes the view that proportionality means that the defending state must do no more than is necessary to halt and repel the attack, and that it is not a question of balancing the harm inflicted by the defensive force against the harm prevented by the defensive force (as Adil nicely expresses it). However, I question whether this is morally justifable in the case of a state that is unable to act.

    7) Olivier suggests that in the case of an armed attack by a non-state actor, the state attacked should be required to seek consent or go to the Security Council. I don’t necessarily disagree. I would simply analyse these issues as part of the necessity requirement. My view is that the so called “unwilling or unable” test is just an aspect of the necessity requirement. However, in my view it does not exhaust necessity. Other factors would also need to be considered. The points Oliver makes, are in my view, some of those other factors. To be clear though, I don’t think consent itself is the key. Simply failing to get a state’s permission does not make it unnecessary to act. However, a state may be unable acting alone but if it can be enabled or assisted then it would be unnecessary to use force without seeking to assist it. So in my view mere inability does not necessarily make it necessary to use force.

  30. Dapo Akande Dapo Akande


    You are right to point out the importance of upholding the principle of no self-defence against self-defence. However, I am not sure that this means that we have to say that the original armed attack must be illegal. Is it not the case that all we need to say is that there is no right of self defence against lawful uses of force? Putting the principle this way would, I think, care of the problem you identify, but it still leaves open the possibility of using force against non-state actors.

  31. Hi Dapo,

    Thanks for that rich reply. Here are a few thoughts in response.

    1) I agree that “self defence is not a legal remedy for implementing responsibility but rather what it says – a means of defending oneself from attack.” In my view, responsibility is not the basis of self-defense but rather identifies who may be harmed as a means of defending oneself from attack.

    To illustrate, suppose that Marko is now attacking Marty. If Marty defends himself from Marko by harming Marko, that is self-defense. In contrast, if Marty defends himself from Marko by using Olivier as a human shield, then that is mere self-preference. Olivier is not responsible for Marko’s attack, and is not liable to be harmed as a means of defending Marty. Accordingly, harm to Olivier would have to be justified on some other grounds (consent, lesser evils, etc).

    2) Of course, you are right that we often say that territory is part of the state and that force used on the territory of the state is used against the state. I wonder if it would be more precise to say that states have a right to their territory and that force used on their territory contravenes that right.

    3) In technical terms, I understand self-defense in terms of rights forfeiture, while you seem to understand self-defense in terms of rights specification. On my view, states have a right against force, which they can lose through responsibility for an armed attack. On your view, states have a right-against-force-except-in-self-defense-or-with-UNSC-authorization. Sadly, I don’t have a knockdown argument for my view and against yours. I just find mine more intuitively appealing.

    4) I agree that these states take the view that self-defense alone justifies the use of force against non-state actors on the territory of other states. I think they’re mistaken, and that supplemental justification (extreme gravity of the attack, loss of territorial control) is required.

    6) I question whether the “no more than necessary” view is morally justifiable in a range of cases! But leave that for now.

    7) I’m attracted to Olivier’s suggestion that necessity requires exhaustion of alternatives to *non-consensual* force. The unwillingness or inability of the territorial state to prevent armed attacks from its territory may or may not entail that force is necessary, as you note, but it certainly does not entail that *non-consensual* force is necessary. To exhaust alternatives to non-consensual force, generally one should actually seek consent.

    Thanks again for your reply. This exchange has been fun and instructive.

    Very best,


  32. Actually, you may enjoy this, from an earlier exchange with Marty (

    You close with a fascinating question: “would (should) it be lawful for Syria to use force against the foreign forces currently operating in its territory, assuming that they are in compliance with both Article 51 and the LOAC?” . . .

    . . . I think the answer depends very much on how we understand jus ad bellum proportionality. In just war theory, a use of force is jus ad bellum proportionate only if it does more good than harm. However, according to the prevailing view in international law, a use of force is jus ad bellum proportionate so long as it is no more than necessary to repel or prevent an armed attack. On this view, it is jus ad bellum proportionate for State A to kill 1,000 civilians in State B to prevent Group G from carrying out periodic armed attacks that each kill no more than five or six civilians in State A. If that is correct, then it seems perfectly plausible that State B would be justified in using force to protect its civilian population from State A. The fact that the prevailing view of jus ad bellum proportionality in international law yields such results, in which both sides appear justified in using force, may be a reason to reject the prevailing view. But I leave that question to the future.

  33. Federica Paddeu

    Hi Dapo,

    I have thought about that option as well, but find it less persuasive

    International law works on a binary deontic logic, in the sense that the result of the legal syllogism is always just one of two options: lawful/unlawful. It seems to me that the armed attack by the NSA is not unlawful. (Veering dangerously close to Lotus) it must, therefore, be lawful. This is not to say they have a legally protected right to engage in it. It is enough for them to have a liberty to do so (liberties are tolerated, but not protected as such by the legal order, to explain it with Hohfeld again). Them having a liberty simply means that there is no other entity of the legal order who has a right that they not engage in that conduct (they have a no-right). So to rely on the legality of the armed attack to uphold the no-self-defence against self-defence principle may ultimately not be of much help.

    This answer of course hinges on international law actually working on this binary deontic logic and that, for example, legal neutrality (as argued by the UK in Kosovo) does not stand. The ICJ assumed this much in Kosovo and was criticised by some judges for it (e.g., Simma). There are theorists who would include such a category (e.g., Stone and some others), but to be honest I have yet to develop views about this (essentially, I need to do more research!). For now, I can point you to Joerg Kammerhofer’s excellent article on gaps in the BYIL (can’t remember the year, and am traveling so can’t get the details now) where he discusses this question. So as my work stands now, I cannot take the argument on this basis any further. But there is potential to say that if the armed attack by the NSA is simply a neutral act, and self-defence is lawful, then this is enough to uphold the principle. (BTW, any help with materials on this issue would be very welcome!)


  34. Dapo Akande Dapo Akande

    Hi Federica,

    While the use of force by non-state actors is not regulated by Art. 2(4) of the Charter and its customary equivalent, I doubt that this means that we can say that the non-state actors have a liberty to use force against states. It is arguable that such conduct is prohibited for non-state actors by some of the rules relating to terrorism. But let us even assume that there is no rule directed at non-state actors that prohibits uses of force against state. Could we then say that their acts are lawful in the sense that they have the liberty to engage in such conduct? I doubt it. States have an obligation to prevent their territory from being used by non-state groups to launch attacks against other states. This must mean that vis a vis the territorial state, the non-state actor has no liberty, as a matter of international law, to engage in this conduct (and this despite the absence of a prohibition directed at the non-state actor). Now, one might say that the lack of a liberty only applies vis a vis the territorial state. However, the beneficiary, and indeed the right holder, in the case of the obligation to suppress such acts is the attacked state. It would be strange to then say that the non-state actor has a liberty to act vis a vis the attacked state.

    My point is that even if international law were not to address a rule to the non-state actor prohibiting it from using force against other states, this does not lead us to the position that international law provides a liberty to act in this way. Or at least it ought not lead us to this position.

  35. Federica Paddeu

    Hi Dapo,

    I think you are right on the positive law point. But given that the reasoning might lead us there (as you say, it ought not, but it could), I think that the illegality of the armed attack remains the safest way to preserve the no-self-defence against self-defence principle. Indeed, we might want both: illegality of armed attack plus legality of self-defence. This is what happens with countermeasures: the triggering measure is illegal, and the response is legal.

    Also, on the state responsibility framework, to require illegality of armed attack does not in itself turn the response into a state responsibility institution. Wrongful acts give rise to consequences which are not caught in the responsibility net–like Art 60 VCLT and nullity.


    Ps: will be off the grid for a few days.

  36. Jordan

    On flaw in the discussion is the contention by some that a use of force in collective self-defense against the NSA ISIS on Syrian territory is a use of force against Syria. As Marty notes, there is historic practice regarding use of force in self-defense against NSAs without state attribution or general opinio that such action is against the territorial state (ok, no SSRN click-on that I have offered many times before on this point). Further, the Nicaragua test is not control but substantial involvement therein (ok, no click-on here, but point made before).

  37. Jordan

    I still find interesting Lord Campbell’s statement regarding The Caroline: we had a clear right to seize and destroy her, just as we might have taken a battery erected by the rebels on the American shore, the guns of which were fired against the Queen’size troops in Navy Island.
    And see Lord Ashburton July 28 to Webster regarding a shore battery. My footnote 19 in 45 Georgetown Journal of International Law (2014).