Gas! GAS! Quick, boys! - An ecstasy of fumbling
Fitting the clumsy helmets just in time,
But someone still was yelling out and stumbling
And flound'ring like a man in fire or lime.-
Dim through the misty panes and thick green light,
As under a green sea, I saw him drowning.

The words of the poet Wilfred Owen captured the horrors of chlorine gas in WWI and the recent events in Syria, with credible allegations of the use of chemical weapons, serve to reinforce the importance of renewed international rigour if their use in conflict is not to become, in the words of The Guardian newspaper, ‘normalised’1.

In the present context, it is timely to remind ourselves of the public international law/international humanitarian law (IHL) framework that addresses this type of weapon. At the same time, it should not be forgotten that the global prohibitions now in place have evolved primarily to ensure that chemical warfare does not have a place on the battlefield and that, most disturbing of all and contrary to the key IHL principle of distinction, the picture emerging from Khan Sheikhoun is one of civilian objects, not military objectives, having been targeted.

It might come as a surprise to some that the first international instrument to address chemical warfare was agreed in 1675, when France and the Holy Roman Empire concluded the Strasbourg Agreement, thereby agreeing to a prohibition on the use of poison-laced bullets. Even more startling, perhaps, is that (putting to one side the Brussels Conference of 1874 that recommended, but never reached a formal agreement on, a prohibition on the use of poisonous and poisoned weapons) it was not until The Hague Convention of 1899 and its ‘Declaration on the Use of Projectiles the Object of Which is the Diffusion of Asphyxiating or Deleterious Gases’2 that States arrived at meaningful agreement on the outlawing of chemical agents in war.

Notwithstanding the strides made in 1899, WWI saw the use of a range of noxious or asphyxiating agents, including chlorine, phosgene and mustard gas, which, in turn, brought about renewed international efforts to prohibit the deployment of chemical weapons. The result was The Geneva Protocol of 1925 that prohibits ‘the use in war of asphyxiating, poisonous or other gases, and of all analogous liquids, materials or devices’ and now amounts to a customary rule3. It does not, however, prohibit the development, manufacture, acquisition or stockpiling of such weapons. Moreover, some States (including the UK) entered reservations to the effect that they would not be bound by the Protocol if the opposing side in a conflict breached the Protocol. For those States, the effect was, in reality, an acceptance of a ‘first use’ prohibition, albeit that some of those reservations were withdrawn (fully or partially) in the light of later obligations contained in the Chemical Weapons Convention (see below).

The period before and during WWII saw much research into and production of chemical weapons, even though there was no deployment on the battlefield in the conflict itself. Meanwhile, the post-war years saw concerns on the part of a number of States grow in respect of both biological and chemical weapons and, in particular, as to development, production and stockpiling. These were crystallised by the Swedish Government, which had both weapons added to the agenda of the 1968 Geneva disarmament conference (the Eighteen Nations Disarmament Committee (ENDC)). In the wake of the conference, however, negotiations diverged, with the Biological Weapons Convention gathering more traction and entering into force in 1975 (having opened for signature in 1972).

Helpfully, the 1975 Convention made provision for further work on chemical weapons by providing (at Article IX) that:

‘Each State Party to this Convention affirms the recognised objective of effective prohibition of Chemical Weapons and, to this end, undertakes to continue negotiations in good faith with a view to reaching early agreement on effective measures for the prohibition of their development, production and stockpiling and for their destruction…’

In the event, the world had to wait until 1992 for the draft text of the UN’s Chemical Weapons Convention (CWC), which was opened for signature in January 1993 and entered into force on 29 April 1997. The CWC is intended to eliminate chemical weapons by prohibiting their development, production, acquisition, stockpiling, retention, transfer or use. For their part, States Parties are obliged to take the steps necessary to enforce that prohibition in respect of both natural and legal persons within their jurisdiction.

The CWC seeks to fulfil its aims by the agreement of States Parties to chemically disarm by destroying any stockpiles of chemical weapons they may hold and any facilities which produced them, as well as any chemical weapons they have abandoned on the territory of other States Parties in the past. In addition, States are obliged to create a verification regime for certain toxic chemicals and their precursors.

One of the key implementation features of the CWC is its 'challenge inspection' regime, by which any State Party that doubts another State Party's compliance with its obligations is able to request the deployment of an inspection team, which works on the basis of any time/anywhere inspections to which there is no right of refusal. The Organisation for the Prohibition of Chemical Weapons (OPCW) is the implementing body of the CWC. For its part, Syria acceded to the CWC in October 2013.

In IHL, the customary position as to the use of chemical weapons in an armed conflict is clear. Rule 74 of the ICRC’s Customary Study states that: ‘The use of chemical weapons is prohibited.’4 In an international armed conflict, the prohibition is also contained in those instruments already referred to, dating back to the Hague Declaration, and is set out in the Rome Statute of the International Criminal Court (ICC) (at Article 8(2)(b)(xviii)). It is also a war crime as a grave breach of the Geneva Conventions (at Article 8(2)(a)) if an attack amounts to wilful murder or wilfully causing great suffering or serious injury, or as a serious violation of the laws and customs of war (at Article 8(2)(b)(i)) as an attack upon the civilian population).

As for non-international armed conflicts, customary Rule 74 bites and, in the words of the Appeals Chamber of the ICTY in Tadic, ‘there undisputedly emerged a general consensus in the international community on the principle that the use of [chemical] weapons is also prohibited in internal armed conflicts’5. As a matter of custom, therefore, the use of chemical weapons in an internal armed conflict amounts to a war crime as a serious violation of IHL (ICRC Customary Study, Rule 156). For ICC purposes, such use is now set out in the 2010 amendment to Article 8(2)(e) (at (xiii) and (xiv)) as a war crime in a non-international armed conflict. It may also amount to a serious violation of Common Article 3 of the Geneva Conventions (now reflected in Article 8 (2)(c) of the Rome Statute) as an act or acts committed against protected persons and a serious violation of the laws and customs of war as an attack on the civilian population (at Article 8(2)(e)(i)).

Understandably, a chemical attack of the sort that has allegedly taken place in Syria6 is sometimes spoken of in the media as a ‘crime against humanity’. Notwithstanding the aptness of that phrase as an expression of moral outrage, it is not necessarily legally correct.

Article 7(1) of the Rome Statute defines a crime against humanity and sets out a list of acts which, when committed as part of a widespread or systematic attack directed against any civilian population, with knowledge of the attack, makes out the offence. That list includes murder and inhumane acts intentionally causing great suffering or serious injury, but does not contain the use of chemical weapons. Of course, if one of the prohibited acts (such as murder) is the consequence of the use of a chemical weapon, then a crime against humanity is capable of being made out, subject, of course, to being able to prove the other elements (for instance, as to the widespread or systematic nature of the attack) contained in 7(1).

We might satisfy ourselves that the conduct alleged amounts to an international crime (be it a war crime or a crime against humanity), but that is likely to count for little if there is no means to secure justice in respect of the perpetrators. Here, undoubted difficulties arise. Syria is not a State Party of the Rome Statute and the only route to ICC jurisdiction would, therefore, be by way of a UN Security Council referral. However, the political reality is that a veto from one of the Permanent 5 (in this case, Russia, certainly) would defeat that process.

Looking into the future, some have suggested, as an alternative, the establishment of an ad hoc international tribunal (in the image of the ICTY and ICTR); however, both the ICTY and ICTR were created under the Chapter VII powers of the Security Council and so the risk of a veto remains! A second option (without recourse to the Security Council) would be to consider a hybrid court that contains a mixture of Syrian and international prosecutors and judges.

However, the obstacles are enormous. The immediate challenge would be creating a credible tribunal that would have both the buy-in and the capability to investigate and prosecute crimes committed by all sides. Added to this, the reality, of course, is that most prominent political actors in a post-conflict Syria are likely to be either implicated in or affected by interests relating to the events that would be under scrutiny. There would then be the more practical, but also politically sensitive, issues of where to locate such a tribunal and how the inevitably large costs would be met.

A tribunal of any sort is perhaps some way into future; the more immediate concern remains whether other states are likely to follow the US military strikes, collectively or individually. At the time of writing, the US has not set out the basis of its action, which could fall under one of two heads: humanitarian intervention or reprisal. The former, although legally contentious, may be legal, whilst the latter (post-1945) is unlawful. Given the obligations and consequences that flow from any military action, on whatever legal basis, it is worthwhile examining the options that are may be available to the international community in the absence of any UN Security Council authorisation. A follow-up PILAG briefing will seek to address this.


1 The Guardian, 16 August 2016

2 Laws of War: Declaration IV, 2 (July 29, 1899) banning ‘the use of projectiles the sole object of which is the diffusion of asphyxiating or deleterious gases’.

3 It is worthy of note that the prohibition contained in the Protocol was the basis for the assertion that the use of chemical weapons in the Iran/Iraq conflict (1980 – 88) was unlawful.

4 Notwithstanding the ‘first use’ reservation referred to in respect of the Geneva Protocol, the ICRC expresses the view that there is increasing evidence that it may also be unlawful to retaliate in kind to the use of a chemical weapon by another State.

5 Prosecutor v Tadic, Case No. 94-1-AR72, Appeal on Jurisdiction, para. 124.

6 For a timeline of attacks allegedly involving chemical weapons, the Arms Control Association provides a useful guide which can be accessed at:



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