The Precedent Set by the US Reprisal Against the Use of Chemical Weapons in Syria

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In his recent post on the United States’ missile strike against a Syrian airbase, on 6 April 2017, Marko Milanovic focused primarily on the unlawfulness of that action (here). While I agree with that view, in this post, I wish to focus on the nature of the precedent which the US reprisal has set. Moreover, I argue that this instance of use of a forcible countermeasure by a permanent member of the UN Security Council (UNSC) should serve to refocus attention on a dysfunctional UNSC.

Three remarks at the outset: (a) This post concerns only “forcible countermeasures” or “reprisals”; (b) I characterise the US missile strikes as a reprisal against Syria’s use of chemical weapons. Although other characterisations have been proffered (for instance, humanitarian intervention or providing assistance in a counter-insurgency), the US administration has framed its actions primarily in terms of a forcible response to the use of chemical weapons (see below); and (c) I rely on the assumption, tendered by the US but disputed by Russia, that Syria was responsible for the chemical attack.

The Legal Framework

A useful starting point for this discussion are the Draft Articles on Responsibility of States for Internationally Wrongful Acts, adopted by the International Law Commission (ILC) in 2001, which have been said to present “a combination of codification and progressive development” (Harris, Cases and Materials on International Law, p. 422). Article 49(1) of the Draft Articles states that “An injured State may only take countermeasures against a State which is responsible for an internationally wrongful act in order to induce that State to comply with its obligations…” Thus, while the Draft Articles envisage the lawfulness of countermeasures in certain circumstances, it is important to clarify briefly: (1) which countermeasures are envisaged; and (2) which party may undertake them.

As regards which countermeasures are envisaged, Article 50 (1)(a) of the Draft Articles states that “(1) Countermeasures shall not affect…(a) the obligation to refrain from the threat or use of force as embodied in the Charter of the United Nations.” Thus, Article 50 prohibits forcible countermeasures or reprisals, and this prohibition is consistent “with prevailing doctrine as well as a number of authoritative pronouncements of international judicial and other bodies” (Harris, Cases and Materials on International Law, p. 457).

As regards which party may undertake the countermeasures envisaged by the Draft Articles, only a state injured by the violation may resort to counter measures against the wrongdoer (Crawford, Brownlie’s Principles of Public International Law, p. 588). Crawford notes that, during the ILC discussions, the question of whether serious breaches of peremptory norms “do not entail a right to take countermeasures in the collective interest” did arise. However, as a result of “strong reactions from many states, concerned in particular with the potential for arbitrariness in imposition of third-party countermeasures”, the possibility for such action was dropped. The result is that there is “no clearly recognized entitlement of [non-injured states] to take countermeasures in the collective interest” (Crawford, p. 588). In any event, however, such an entitlement would only have related to non-forcible countermeasures, and not the type of forcible countermeasures with which this post is concerned.

Therefore, the prevailing view is that there is a general prohibition of forcible countermeasures or reprisals in the lex lata. As Milanovic noted, “[i]nternational law does not permit forcible reprisals that would breach Article 2(4).” This position is shared by most international lawyers (see Gardam, Necessity, Proportionality and the Use of Force by States, p. 140). One reason for this is that “…many reprisals may lead to a chain of violent conduct and counter-reprisals. This dangerous potential becomes evident when reprisals are used as a form of revenge” (see Mitchell, “Does one illegality merit another? The law of belligerent reprisals in international law” 155 Military Law Review (2001) p. 172).

Admittedly, in Nicaragua, the Court appeared to have left the door open for some lower-level, smaller-scale forcible countermeasures on the part of the injured State (Nicaragua, ICJ Reports 1986, p. 127, para. 249). In his separate opinion in Oil Platforms, Judge Simma observed that, in Nicaragua:

“the Court drew a distinction between measures taken in legitimate self-defence on the basis of Article 51 of the Charter and lower-level, smaller-scale proportionate counter-measures which do not need to be based on that provision…” (Oil Platforms, ICJ Reports 2003 – Separate Opinion of Judge Simma, p. 332).

However, this possibility is not considered further in this post, because I do not consider that the US reprisal of 6 April 2017 (discussed below) could be characterised as lower-level and smaller-scale, in accordance with the understanding of that case.

The US reprisal

The US strikes against Syria were undertaken in reprisal for the “worst chemical attack in years in Syria”, on 4 April 2017, as a result of which “[d]ozens of people, including children, died – some writhing, choking, gasping or foaming at the mouth” (see here). In a statement of 6 April 2017, President Trump stated:

My fellow Americans: On Tuesday, Syrian dictator Bashar al-Assad launched a horrible chemical weapons attack on innocent civilians. Using a deadly nerve agent, Assad choked out the lives of helpless men, women, and children. It was a slow and brutal death for so many. Even beautiful babies were cruelly murdered in this very barbaric attack. No child of God should ever suffer such horror.

Tonight, I ordered a targeted military strike on the airfield in Syria from where the chemical attack was launched. It is in this vital national security interest of the United States to prevent and deter the spread and use of deadly chemical weapons. There can be no dispute that Syria used banned chemical weapons, violated its obligations under the Chemical Weapons Convention, and ignored the urging of the U.N. Security Council.

The following day, the US Secretary of State, Tillerson further explained that:

“this particular strike that was carried out on the airbase from which the chemical weapons attack was launched was very deliberately considered by the President. It is a response that we believe is both proportional and appropriate” (see here).

From an evaluation of the available facts, on 6 April 2017, the US used force against Syria in reprisal for Syria’s use of chemical weapons, contrary to Article 1 of the Chemical Weapons Convention, 1993 (“CWC”). Article 1 of the CWC requires States Parties “never under any circumstances: (a) To develop, produce, otherwise acquire, stockpile or retain chemical weapons, or transfer, directly or indirectly, chemical weapons to anyone; (b) To use chemical weapons…” The CWC entered into force in Syria on 14 October 2013 (see here). Moreover, in view of its almost universal acceptance, this prohibition is considered to reflect customary international law.

It is submitted that the US reprisal of 6 April 2017 was in contravention of the general prohibition of forcible countermeasures or reprisals discussed above. Even though it was undertaken in response to another internationally wrongful act (Syria’s breach of the prohibition of the use of chemical weapons), both of these actions were unlawful in the lex lata. In this respect, even though there has been discussion of whether the law on the use of force should be changed (see here and here), that is a separate issue.

However, it is not sufficient to state that the US reprisal was unlawful and stop there. I think, particularly with an eye to precedent, it is necessary to carefully consider the discrete nature of the precedent set by the US reprisal, particularly, in view of its potential longer term impact on Article 2(4) of the UN Charter.

Firstly, the reprisal was undertaken in a context where the UNSC (and the possibility for collective action) was stultified by veto. That the permanent members of the UNSC could not find common ground and take collective action in the face of something as egregious as the use of chemical weapons is troubling, and an issue I will return to in the conclusion. Secondly, the reprisal was undertaken in response to the use of chemical weapons, in flagrant breach of the international prohibition on the use of such weapons. Thirdly, the reprisal was proportionate and characterised by restraint, both in terms of its official description and the facts on the ground. President Trump spoke of “a targeted military strike” and Secretary Tillerson referred to a “proportional and appropriate” response. Although it is difficult to measure proportionality in such cases (see Gardam, p. 155), the military strikes where limited with respect to geography and destructive scope, limited with respect to temporal scope, and specifically targeted the infrastructure (airfield) from where the chemical attack was allegedly launched. Fourthly, the effects of the US reprisal was, in the terms of Gabčíkovo-Nagymaros Project, reversible (Gabčíkovo-Nagymaros Project, ICJ Reports 1997, p. 7 at pp.56-57). It was undertaken in the dead of night and, from the available information, did not involve loss of life – but destruction of infrastructure.

Finally, this reprisal had to be seen in a context where there existed the very real risk that Syria would use chemical weapons against its own population again with impunity, as it had already done in the past. The US considered itself directly “injured” by such action in view, in the words of President Trump, of the “vital national security interest of the United States to prevent and deter the spread and use of deadly chemical weapons.” In this connection, it is notable that, during the Second World War, President Roosevelt threatened reprisals against the Axis Powers if they used poison gas, and some have argued that this threat compelled the Axis Powers to refrain from using poison gas in the battlefield although, as is well known, the tragic history of use of Zyklon B in the gas chambers is well-documented (see Mitchell, p.171). If (and only time will tell) the US reprisal has the effect of forestalling repeated use of chemical weapons in Syria then, on balance, it is not a bad result for international law.

This does not in any way detract from the international wrongfulness of US action. It is also true that this action may have served to undermine the prohibition on the use of force in Article 2(4) of the UN Charter. It is arguable, however, that the alternative of watching idly in the face of repeated uses of chemical weapons would also have eaten away at the core of international law. The choice lied somewhere on the spectrum between Captain Vere’s strict adherence to the law “however pitilessly that law may operate” (Melville, Billy Budd) and Thoreau’s invocation that “we should be men first, and subjects afterward. It is not desirable to cultivate a respect for the law, so much as for the right” (Thoreau, Civil Disobedience).

In this respect, I agree with Franck that “[l]aw is strengthened when it avoids absurdly rigid absolutes” (Franck, Recourse to Force: State Action Against Threats and Armed Attacks, p. 172). In the domestic sphere, Franck referred to the cases of Regina v. Dudley and Stephens (14 QBD 273 (1884)) and United States v. Holmes (26 Fed. Cas. 360, 1 Wall Jr. 1 (1842)) as instances where “law in some limited circumstances may condone or excuse with what is required by law in every circumstances” (Franck, p.173). I agree with his general argument that, in some limited circumstances, unlawful behaviour may be mitigated in view of certain extenuating or mitigating factors. This is different from suggesting, as has sometimes been the case with respect to humanitarian intervention, that certain behaviour should be considered legal because it is legitimate or, indeed, conflating the two concepts (see here).

My view is that, in the lex lata, the US reprisal of 6 April 2017 was unlawful. However, in view of the extenuating circumstances discussed above and, in particular, Syria’s egregious use of chemical weapons, there could be grounds for mitigation. After all, as Franck noted:

“[w]hen law permits or even requires behaviour that is widely held to be unfair, immoral or unjust, it is not only persons but also the law that suffers. So, too, if the law prohibits that which is widely believed to be just and moral” (see Franck, p. 178).

In conclusion, this case should serve to refocus attention on the (dys)functioning of the UNSC and its inability to act in face of egregious threats to international peace and security when the interests of one of the permanent members (or its allies) are invested. This has perpetuated a structural deficiency in the international legal framework which has a direct impact on other elements of the UN Charter, including Article 2(4). There is no easy solution. While comprehensive reform of the UNSC may be out of reach for the present, international lawyers should continue to make sure the matter remains on the international agenda and to lobby for “pragmatic modifications in the Security Council’s working methods” (Weiss, “The Illusion of UN Security Council Reform” 26 The Washington Quarterly, (2003), p.154).

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Kriangsak Kittichaisaree says

May 1, 2017

Since the ILC's Draft Articles on State Responsibility have been cited umpteen times in the discussions on this and other topics, please let me share with you the views of States re: Draft Articles.

On 13, 19, and 21 Oct. 2016, the working group of the Sixth Committee of the UNGA met to consider the fate of the Draft Article -- this kind of session is held every 3 years.
- An increasing number of delegations (including Russia, Algeria, Portugal, Iran, Mexico, African Group of States) favoured moving towards the negotiation of a convention based on the Draft Articles.
- However, some delegations argued that there would be no need for such a convention, as the articles would be more valuable in their current form.
- Some delegations argued that it would be premature to consider the entirety of the articles as settled rules of customary international law, and that State practice itself should be allowed to evolve. (But Greece: most of the Draft Articles codify customary IL.)
- Some delegations feared that a convention which would not be universally ratified would risk 'de-codification' of the Draft Articles.
- NB: US, Canada, Australia, and New Zealand considered the Draft Articles to be 'guidelines' to be considered by States or international courts. The UK: State practice is still evolving in this area and there are certain aspects of the Draft Articles that have elements of uncertainty and are subjected to disputes/controversy; hence, no customary IL on these aspects. Singapore: worried about the negative implications of the Draft Articles, esp. re: countermeasures which are complex and should be left to 'specialist forums' to decide. China: certain Draft Articles are controversial for UN Member States, including those on serious violations of jus cogens obligations and measures to be taken by other States than those directly injured.

Hope the above info is helpful...

John R Morss says

May 1, 2017

Important issues ...(although nb I don't think a reprisal can be 'proportionate'. That's a category error or something?)

Roger O'Keefe says

May 1, 2017

Dear All
At the risk of sounding pedantic and irascible, CAN WE PLEASE STOP CALLING THEM THE 'DRAFT' ARTICLES? They are no longer 'draft'!!! In para 3 of GA res 56/83, 12 December 2001, when taken note of by the General Assembly, they become - textually and thenceforth more generally - the 'articles', no longer draft. That countless scholars fail to appreciate this is probably linked to the fact that the version available in freestanding form online takes its title from the ILC's title, i.e. 'Draft articles'. The same thing happened to the formerly draft articles on diplomatic protection via para 3 of GA res 62/67, 6 December 2007, in which the General Assembly commends the 'articles' to states, and to the formerly draft articles on responsibility of international organizations in para 3 of GA res 66/100, 9 December 2011, in which the General Assembly 'takes note' of the 'articles'. None of these is any longer 'draft'.
Aaaah, that felt good!
Best wishes to all for 1 May.

Mary Ellen O'Connell says

May 1, 2017

John Morss is correct in my view: Trying to analyze military reprisals as 'countermeasures' is a category error. Reprisals aim to punish. Countermeasures aim at restoring legality going forward--ending an on-going wrong or procuring a remedy for the wrong. Countermeasures must be proportionate but also necessary, meaning they are a last resort and have a chance of succeeding. The vague deterrence Trump might have been seeking is far too uncertain to meet these requirements.

More significantly, military reprisals are taken with the knowledge they will result in death and destruction--that result takes them out of the category of lawful countermeasures and places them squarely in the jus ad bellum. In that category, they are unlawful.

Reprisals have been specifically prohibited in the Declaration on Friendly Relations, so no one should doubt their illegality.

Nor are analogies appropriate between civil disobedience of the type Thoreau contemplated and action that results in the violent death of others. Marko provided a film clip of Gandhi taking responsibility for violence by his followers. Gandhi did not carry out the violence himself. It was an unintended consequence that he very much regretted. Trump, by glaring contrast, is personally responsible for 59 cruise missiles striking Syria and the deaths and destruction they caused. Trump is no Gandhi. Trump's attacks were not civil disobedience.

I made a similar reply to Tom Franck following his attempt at analogizing the Kosovo intervention to civil disobedience. The anti-drone protesters in the U.S. being arrested for trespass on military bases are trying to save lives. The ethic of civil disobedience wholly rejects killing.

The correct category for Trump's attack is, as Federica Paddeu persuasively argues in her reply on humanitarian intervention, jus cogens. Peremptory norms demand compliance--lawful countermeasures, not involving the unlawful use of military force would be an excellent means of getting it.

Alessandra Asteriti says

May 1, 2017

This is a serious doubt: can the actions of a clearly unstable leader constitute valid precedent? I am not sure the 'actions' of Donald Trump deserve all the ink that has been spilled either to criticise them on legal grounds, or justify them on legitimacy grounds. To me, it is not too far from responding to the statement of a madman claiming to be Napoleon. Trump is a legal and political aberration. Debating the deficiencies of the UNSC is another matter, obviously.

John R Morss says

May 2, 2017

On re-watching the(in my opinion)very fine McDonagh movie Calvary, I think I saw that the book delivered to the elderly (US?) man by Father James is the HHhH book about the WWII assassination of Heydrich and, presumably, the mass reprisals that followed (apologies, I have not read the book). That raises quite a few relevant questions I think. Reprisals I think can safely be categorised as evil, and 'those to whom evil is done/Do evil in return'.

federico says

May 2, 2017

The US is not an injured State in this occasion.

Kriangsak Kittichaisaree says

May 2, 2017

My reply to Roger's frustration and reminder:

Roger is absolutely correct that the ILC's work on that topic is now OFFICIALLY no longer in a draft form, but 'Articles on ...'. The UN/ILC Secretariat makes sure that this terminology is used in all UN official documents.

I very much hesitated whether I should react to Roger's post at all. But readers may wonder why a former-ILC member like myself still uses the term 'Draft Articles'. In fact, during the period 2012-2016 when I served in the ILC, the ILC discussed the use of 'Draft Articles'/'Articles' a few time, albeit briefly, during closed sessions not open to the public (e.g., the Working Group on the Long-Term Programme of Work; and the Planning Group). So, I cannot disclose how the discussions went.

I can only tell you my personal view -- so long as the ILC's work in the format of draft articles are not picked up by the UNGA and acted upon by, e.g., turning them into 'articles' in an international convention, they remain 'draft articles' and SOMETHING must be done to them. In my latest book 'Public International Law of Cyberspace' published in March 2017, I use 'Draft Articles' throughout. Admittedly, this defiance is not the official position of the ILC Secretariat. It is a reminder that our work just can't be shelved, ignored etc...

Maybe I will use 'Articles' in my next book.

Roger O'Keefe says

May 2, 2017

Dear Kriangsak
Thanks for your kind, enlightening and very interesting post. A rebel with a cause!
I guess the General Assembly's reasoning would be that, once the articles are annexed to a UNGA resolution and 'noted', 'commended' or what have you by the Assembly itself, they cease to be a work-in-progress as far as the ILC is concerned. Of course, as soon as the ILC itself has finally adopted them on second reading, 'draft articles' are in a sense finalised, albeit still 'draft'. The point, however, I guess, is that there is nothing to stop the General Assembly from begging to disagree and sending finally adopted draft articles back to the ILC for further work.
This does not mean that nothing further happens to 'articles', as you helpfully underline. It is just that anything that may happen to them from then on renders them something else, e.g. a draft treaty.
But this is all pure pedantry on my part. More importantly, many thanks and keep us all posted, please!
Warm wishes

Marko Milanovic says

May 2, 2017

Dear Roger and Kriangsak - this blog revels in nerdom and pedantry. You guys rock! Much obliged,


Nicolas Boeglin says

May 3, 2017

Dear colleagues

Many thanks for this extremely useful note and the very valuable information provided.

Concerning specifically US missile strike to be considered as a "precedent", some details have to be pointed out. One one hand, we cannot consider US as an "injured" State. But on another hand, the direct responsability of Syria in the use of chemical substances is something based on lack of evidence.

After almost one month since the event in Idelib, there is no evidence nor an indenpendant investigation made in situ demonstrating the direct responsability of Syrian authorities in the use of chemical substances last April 4. In this case, we have a military strike ordered 48 hours after the event and based on assumptions. And only assumptions.

If we read the draft resolution presented by France, United Kingdom and United States last April 12 at UNSC (and vetoed by Russia), Operative Paragraph 1 says that the Security Council:
“1. Condamne avec la plus grande fermeté l’emploi qui aurait été fait
d’armes chimiques en République arabe syrienne” / “Condemns in the strongest terms the reported use of chemical weapons in
the Syrian Arab Republic” /” Condena en los términos más enérgicos el presunto empleo de armas
químicas en la República Árabe Siria”.

I added the Spanish version due to the fact that “presunto” is closer to “alleged” that “reported”. Maybe our colleagues can find interesting wording in Russian, Arabic and Chinese official version of the draft resolution availabe here:

Anyway, the point is that, despite political discourses heard in France, in US and UK on the direct responsability of Syria in the “chemical weapon attack”, their representatives at UNSC presented a draft resolution trying to force UNSC to condemn the use “reported” or “qui aurait été fait” of chemical weapons.

I wonder if in case of adoption of the resolution, it wouldn´t have been a very first “premiere” in UNSC practice and I take the opportunity to ask to our colleagues if there is any precedent of a UNSC resolution condemning "in the strongest terms" “reported” facts or violence that some of you would like to share with us.

Sincerely yours

Nicolas Boeglin

Aldo Zammit Borda says

May 3, 2017

Dear all,

Thank you all for the important points in the comments section. I just wished to provide some further reflections here:

Dear Kriangsak and Roger,

I think these clarifications on the (Draft) Articles are really helpful. I fully take Roger’s point – in this comment, by way of compromise, I’ll refer to them as bracketed (Draft) Articles, as I agree, adoption by the General Assembly elevates them from ‘draft’ status, but does not endow them with the legal quality of legal ‘articles.’ Thank you, Kriangsak, for your insights on these (Draft) Articles! That was really interesting!

Dear John, Mary and Federico,

I do not think we have a dispute. The US reprisal in this case does not fall within the category of countermeasures. The (Draft) Articles are not applicable here. In particular, Article 42 is not applicable, not least because of the exclusion of force in Article 50 and the fact that, in any event, the US was not an “injured State” within the meaning of Article 42.

The discussion on countermeasures, in my view, provided a useful starting point (only to exclude its applicability in this case) because the US rhetoric in this case was framed in terms similar to countermeasures, i.e. “If a situation arises which, in one State’s view, results in the violation of an international obligation by another State, the first State is entitled, within the limits set by the general rules of international law pertaining to the use of armed force, to affirm rights though counter-measures.” (Air Service Agreement (1978) 18 RIAA 417, 443).

Again, I cite this case only for the limited purpose of stating that, arguably, there is an analogy between how the US framed its actions and the above definition. However, I stress that the categorisation of ‘countermeasures’ is not applicable to the US reprisal.

But my fundamental difficulty remains in this case. It was an unlawful use of force. But, without suggesting that Trump is Gandhi, this targeted reprisal may have strengthened the prohibition on the use of chemical weapons in international law. Moreover, it was characterised by restraint and, as far as I am aware, it did not cause civilian deaths. the US administration followed this action up by imposing sanctions (

As a lawyer, I find this unlawful use of force troubling. But I am also struggling to think of what alternative lawful countermeasures would have been effective and/or whether it would have been benefitted international law to do nothing at all.

John R Morss says

May 5, 2017

Many thanks Aldo. We do indeed need to think outside the square and not be hidebound by our definitional comfort zones... However I still feel it to be a wrong move to describe any reprisal as restrained... Perhaps we should in any case pay more attention to how we define reprisals. The Caroline incident was arguably reprisal (?)...US military responses to 9/11, ditto?