Guest Post: Air Strikes in Syria–Questions Surrounding the Necessity and Proportionality Requirements in the Exercise of Self-Defense

by Sina Etezazian

[Sina Etezazian serves as regional coordinator for the Digest of State Practice at the Journal on the Use of Force and International Law. He is also a PhD candidate at Monash Law School, where he is researching the necessity and proportionality criteria for the exercise of self-defense in international law.]

The lawfulness of conducting air strikes against the Islamic State Group (IS) in Syria is attracting increasing scrutiny from legal commentators. This scrutiny has intensified markedly (for example, see here, here, here, and here) since the UK’s targeting of alleged IS terrorists using drones and France’s joining the air campaign to bomb IS positions in Syrian territory. The extent to which air strikes would meet the necessity and proportionality requirements in the exercise of the right to self-defense under Article 51, however, remains less explored.

This post does not aim to consider the issue of the permissibility of engaging in unilateral forcible measures against unattributable attacks by private groups. However, even assuming that the lawful exercise of the right of self-defense extends to action against irregular forces, it can be argued that the air campaign in Syria goes beyond the necessity and proportionality conditions of defensive force.

First, the operation in Syria would appear to act in direct contradiction to the legal obligations attached to the “no choice of means” criterion of necessity. As I have explained before (see here and here), “no choice of means” — or, as most legal writers have referred to it, the “last resort” — as a condition inherent in the necessity requirement, denotes that self-defense is available to the victim state only when measures not involving force are unlikely to be practicable and effective to cease an actual armed attack (or prevent an impending attack, supposing that one accepts the idea of anticipatory self-defense). This implies that if measures other than force are likely to be practicable in redressing the wrong caused by the attacker, the victim state may not be entitled to use force under Article 51.

An exploration of state practice since the establishment of the UN would suggest that, in several instances (see here, here, and here), the claimant state highlighted its alleged failed attempts to convince the territorial state to suppress the activities of the non-state entities acting from that state, so as to prove that its self-defense action against those entities had satisfied the necessary requirement. Therefore, whatever the legal merit of the actions themselves (and regardless of whether, in practice, the responding states authentically used force outside an inter-state context), adherence to the “no choice of means” requirement can be distilled from state practice during the UN-era.

Conversely, most states carrying out air strikes in Syria did not even consider cooperating with the Syrian government in suppressing the activities of IS militants in Syria. The United States, for example, explicitly rejected a request for such cooperation, maintaining that it is “not looking for the approval of the Syrian regime.” In its letter to the Security, Canada likewise stated that “in expanding our airstrikes into Syria, the government has now decided we will not seek the express consent of the Syrian government.” The approach taken by US and Canadian officials appears to be in clear violation of the necessity condition of defensive action, mainly because the US and Canada have not provided an explanation of why cooperating with the Syrian government seems impracticable to settle the problem. The use of force in Syria, accordingly, hardly seems compatible with the concept of “no choice of means” that states have shared during the UN-era.

As for proportionality, the air campaign in Syria may be seen to have contravened the geographical requirement inherent in proportionate self-defense. Under the contemporary jus ad bellum regime, defensive action must conform to three criteria to determine its proportionality with regard to a primary objective of halting the attack: effects on civilians, the geographical scope and temporal duration of the conflict (Judith Gardam, Necessity, Proportionality and the Use of Force by States (2004) 155–187). The second of these criteria, usually called the geographical criterion of proportionality, means that forcible self-defensive measures must be limited to the region of the attack that they are designed to repel. In other words, any coercive action that occurs far from the initial attack is likely to constitute a disproportionate use of force (Christopher Greenwood, ‘Self-Defence and the Conduct of International Armed Conflicts’ in International Law at a Time of Perplexity, Yoram Dinstein (ed) (1989) 276–278).

Observance of the geographical criterion of proportionality has been required by both state practice and ICJ jurisprudence (see examples from state practice in Gardam, Necessity, Proportionality and the Use of Force by States, 162–167). For example, in the Armed Activities case, the Court refuted Uganda’s claim of self-defense against attacks from the private groups based in the Eastern Democratic Republic of Congo (DRC). More concretely, Uganda asserted that a string of attacks that had been mounted by those private groups across its border had justified Uganda’s right to use force in self-defense. However, Uganda had taken airports and towns in the DRC, which were located “many hundred kilometers” from Uganda’s border. This extensive forcible response gave rise to the majority judgment observing that the measures undertaken by Ugandan forces were disproportionate to those alleged cross-border attacks (Armed Activities on the Territory of the Congo (Democratic Republic of the Congo v Uganda) (Judgment) [2005] ICJ Rep 223, 223).

However, some commentators have occasionally argued for the diminishing role of the geographical criterion in the assessment of proportionate self-defense, particularly when the situation encompasses the use of force against non-state actors. Thus, in the words of Tams and Devaney:

[R]ecent practice suggests that geographical factors that may be considered relevant to the proportionality of inter-state self-defence are of limited relevance: hence states hit by terrorist attacks on their home soil have asserted a right to respond against terrorists at their base – and even where their conduct was not generally accepted, the fact that the self-defence operation had carried the fight against terrorism into far-away, remote countries seemed to be a factor of limited relevance (Christian J Tams and James G Devaney, ‘Applying Necessity and Proportionality to Anti-Terrorist Self Defence’ (2012) Israel Law Review 94, 104).

Recent suggests that geographical factors that may be considered relevant to the proportionality of inter-state self-defence are of limited relevance: hence states hit by terrorist attacks on their home soil have asserted a right to respond against terrorists at their base – and even where their conduct was not generally accepted, the fact that the self-defence operation had carried the fight against terrorism into far-away, remote countries seemed to be a factor of limited relevance.

Such analysis of the relevant law could be taken as offering justification for relaxing the geographical criterion of proportionality. Admittedly, the geographical criterion must be reasonably applied with some degree of flexibility in the age of terrorism. Nevertheless, the well-accepted rules that have defined the content of proportionate self-defense under modern jus ad bellum do not tend to reinforce the argument of Tams and Devaney concerning the relationship between geography and self-defense actions against irregular forces. By way of contrast, several examples can be found during the UN era where a state condemned the remoteness of the response taken in self-defense against both state and non-state actors. For example, when the US claimed that its 1986 aerial bombing of Libyan territory had been validly undertaken in response to imminent attacks from Libyan-sponsored terrorists (UN SCOR, 2674th mtg, UN Doc S/PV.2674 (15 April 1986); Stanimir A. Alexandrov, Self-Defense Against the Use of Force in International Law (1996) 184–6), Libya disputed the US’s claim of self-defense by questioning the geographical extent of the response (UN SCOR, 2671st mtg, UN Docs S/PV.2671 (31 March 1986) 38. Likewise, in 2005 Jordan underlined the role of geography when seeking to maintain that Israel’s construction of the security wall in the occupied territories had been disproportionate under Article 51 of the UN Charter (Written Statement Submitted by The Hashemite Kingdom of Jordan, Legal Consequences of the Construction of a Wall in the Occupied Palestinian Territories (Advisory Opinion) [2004] 141–2). The geographical criterion of proportionate self-defense thus appears to represent an established rule of customary international law. For this reason, the fact that states have refused to appeal to the geographical criterion of proportionality when reacting to the most recent examples of claimed self-defense actions against non-state entities would not imply that this criterion is of limited relevance in these cases. State practice (and corresponding opinion juris) accordingly provides a rebuttal to the arguments of Tam and Devaney regarding the geographical features of proportionate self-defense.

The manner in which France and Canada have framed their legal arguments to join the air campaign in Syria may indicate that the use of force against IS targets in Syrian territory has evolved towards an attempt to bypass the geographical criterion for proportionality. Canada, for example, has tried to couch its action in Syria not only as a component in the collective self-defense of Iraq but also as action undertaken in response to “a threat” that it has asserted IS poses to “Canada and Canadians, as well as to other countries in the region and beyond”. French Foreign Minister Laurent Fabius has put forward a similar argument:

As soon as it is established that from Syrian territory, which is not entirely controlled by the Syrian government.… Daesh forces (another term for the Islamic State group) are threatening French interests, both outside and inside France, it is perfectly legitimate that we defend ourselves.

Also, on 27 September, French Prime Minister Manuel Valls stated that France had carried out its first strike against IS in Syria, providing the same self-defence justification as that advanced by the French Foreign Minister: “We are hitting Daesh because this terrorist organisation prepares its attacks against France from Syria. We are acting in self-defence.”

From these statements, it can be inferred that both France and Canada have endeavored to provide justification for intervening militarily in Syria, based on the attacks they alleged IS may launch against them in the future. In both statements, self-defense has been invoked to justify using force in Syria that is far removed from the areas of the alleged future attacks (France and Canada).

Leaving aside the question of immediacy, it would seem that such statements have nothing to do with the collective self-defense of Iraq, but rather amount to an invocation of individual self-defense that would run counter to the geographical standards set down by the proportionality requirement. Indeed, when states claim such an expansive view of proportionality, the objective standard against which to measure proportionate self-defense becomes unconstrained. The question then arises of whether the given case continues to conform to the proportionality requirement. The same situation appears to be true of the US-led operation in Syria, where the recent trend in the practice of the states now joining the operation shows that it has been geared almost towards an overt breach of the geographical requirement contained in jus ad bellum self-defense. In this way, the air campaign can be seen as amounting to a series of coercive measures that hardly meet the aim of proportionality: halting and repelling an attack.

6 Responses

  1. I have two questiond:Can the air strikes be justified on the basis of that UN chapter which permits military intervention when international peace and security are in danger?
    2) are those aprinciples you are relying on to examine whether the air strikes are legaly justifiable applicable when non-states or failed states are involved ? Is syria or isis a state , or they should be regarded failed state as seemingly the american do so ?

  2. Both of these alleged limitations are to strict in terms of actual patterns of practice re: targeting NSAs who are engaged in ongoing processes of armed attacks emanating from another state and in terms of general patterns of opinio juris. As you point out, “necessity” is most relevant to claims to engage in “anticipatory self-defense” before an armed attack or series of armed attacks is underway. Once there is an armed attack or series of armed attacks, necessity will most likely be met (re: practice and opinio). Proportionality is a different matter, as you point out.
    However, it would seem to be generally accepted practice to target the NSAs who are directly participating in the armed attacks (and who are, therefore, targetable DPAAs — see and )wherever they are located.

  3. Thanks for that comprehensive post . The author of the post insists on the obligation of the state attacking, to obtain first the consent or the cooperation , of the lets say: ” disintegrated state “, like Syria.

    Yet , the respectable author, doesn’t deal with simple issue :

    Why would Syria for example , being able , Prima facie , to do for the US for example , what it can’t do , prima facie for itself ? for its own survival !! Syria by itself, fights Daesh , for example, surely, not with very impressive success ( in understatement ) .

    Also to notice :

    Suppose that a request for consent is delivered, wouldn’t it mean, that, the state attacking, is recognizing the sovereignty and full integrity of the ” disintegrated state “?? if so , then , a decline , is obliging !! And why to do that , while prima facie the ” disintegrated state ” is not competent , for its own survival ??

    I think ignoring such questions , may not contribute for better just practicality in this regard .


  4. While a state has an inherent right of self-defence when an armed attack occurs, the most part of the scholars is moving from a position strictly connected to the prescriptions of the Charter to another questing a more realistic vision of today’s menaces. Assuming there must be some degree of imminence, disagreement remains on what imminence is. Accordingly, the core question on how distinguishing aggression from self-defence remains, while the disagreement favours unilateralist approaches which are usually perceived as attempts to twist a set of rules created by the community into a system prone to the pure egoistic interest of the power involved.

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