Chemical Weapons and The ICC

Can the International Criminal Court start prosecuting for the use and supply of chemical weapons? Sheryn Omeri considers the ICC’s options.

The centenary of the start of World War I reminded us that it will soon be the centenary of the use of poison gas in international warfare.

But even the clearest statement in international law has not managed to prevent its use in our own time. In March 1988, the government of Saddam Hussein used chemical weapons against Kurds living in the Iraqi town of Halabja in what remains the largest chemical weapons attack against a civilian population in history. In 2013, chemical weapons were used in the conflict in Syria. More recently, in July 2014, Syrian Kurds fighting against the Islamic State (ISIS) were gassed.

Given the gruesome effects of chemical weapons upon victims, it is surprising that to date the International Criminal Court (ICC) has not prosecuted a single case involving their use. It is time to consider whether the Office of the Prosecutor should now begin such prosecutions, and how it may do so.

Does the Rome Statute enable prosecution?

Article 5 of the Rome Statute limits the ICC’s jurisdiction to the most serious crimes of concern to the international community as a whole; namely genocide, crimes against humanity, war crimes and crimes of aggression. The use of chemical weapons falls most readily within the definition of war crimes, set out in Art 8 – see box, right. In 2010, the Kampala Review Conference adopted an amendment to Art 8(2)(e) which extended the list of war crimes in armed conflicts of non-international character to include those set out at Art 8(2)(b)(xvii) and (xviii).

The gassings of the Kurds at Halabja in 1988 amounted to an armed conflict ‘of an international character’ given that they occurred in the context of the eight-year war between Iran and Iraq. (However, Art 11(1) of the Rome Statute limits the jurisdiction of the ICC to crimes committed after its entry into force on 1 July 2002.)

The conflict involving ISIS must also be of an international character. The August 2013 gassings in Syria, however, did not occur in the context of an armed conflict of an international character, thereby rendering Art 8(2)(c) most relevant. As Syria is not a party to the Rome Statute, any members of ISIS responsible for the use of chemical weapons in 2014, or President Assad, could only be prosecuted if the chemical weapons attacks in Syria were referred to the Prosecutor by the Security Council.

Assuming such referral would be made, scholars are divided as to whether Art 8(2)(b)(xvii) and (xviii) (and now 8(2)(e)) include chemical weapons. Arguably this does not matter, however, since where the use of chemical weapons causes death or great suffering, a prosecution may be brought. An attempt at a referral in relation to the Syrian civil war more broadly was made in May 2014, when Security Council members China and Russia vetoed the relevant draft resolution. But given both historical and contemporary recognition of the nefarious nature of chemical weapons, the effects of which have the potential to span generations, it is worth considering whether a prosecution could be brought specifically for the use of chemical weapons.

Such international prosecution would accord with global resolve to prevent the use of chemical weapons manifested in the Protocol for the Prohibition of the Use of Asphyxiating, Poisonous or Other Gases, and of Bacteriological Methods of Warfare (the 1925 Geneva Protocol, from which the Rome Statute takes its wording), the 1993 Chemical Weapons Convention, and the continued existence of the Organisation for the Prohibition of Chemical Weapons. Indeed, it has been recognised that the prohibition on chemical weapons has attained the status of customary international law. (See K Allen, S Spence and R E Leal, “Chemical and biological weapons use in the Rome Statute: a case for change” (February 2011) Vertic Brief 14.)

However, some contend that Art 8(2)(b)(xvii) and (xviii) do not include the use of chemical weapons because of a quirk of the statute’s drafting history. At the time of drafting, some participating countries were of the view that since chemical weapons were the “poor person’s” weapons of mass destruction (as distinct from nuclear weapons), deliberate omission of nuclear weapons from the Rome Statute should be accompanied by deliberate omission of chemical weapons. Hence, on 17 July 1998, the last day of negotiations, mention of chemical, biological and nuclear weapons was dropped from the final proposed draft of the statute.

Does the drafting history matter?

Drafting history is largely irrelevant to the question of whether those responsible for the use of chemical weapons in Syria in 2013 and 2014 can be prosecuted specifically for this. Article 31(1) of the Vienna Convention on the Law of Treaties states: “A treaty shall be interpreted in good faith in accordance with the ordinary meaning to be given to the terms of the words in their context and in the light of its object and purpose.”

Context, object and purpose are not to be gleaned from a treaty’s drafting history. In this regard, Art 32 refers to recourse being had to supplementary means of interpretation, including the circumstances of a Treaty’s conclusion, only when interpretation according to Art 31 leaves the meaning of a provision ambiguous or obscure or leads to a result which is manifestly unreasonable. On their face, Art 8(2)(b)(xvii) and (xviii) are not ambiguous or obscure. It must be beyond doubt that mustard gas and sarin which cause choking that may or may not lead to death in a particular case, are capable of doing so and are therefore each an “asphyxiating gas”. The war crime is “employing asphyxiating gas” not “asphyxiating with gas”.

Do the Kampala amendments permit prosecution?

Article 121(5) of the Rome Statute indicates that amendments to Art 8 only enter into force for state parties that have accepted them. The ICC has no jurisdiction to prosecute crimes committed by the nationals of state parties that have not accepted an amendment, or on such state parties’ territories.

In the case of the use of chemical weapons in the internal armed conflict in Syria in 2013, the key lies in the possibility of a Security Council referral. Such referral must be for consideration by the Prosecutor in accordance with the terms of the Rome Statute as at the time of referral. In accordance with Art 121(3), amendments are adopted by a two-thirds majority of state parties voting in favour of them. Once this vote has carried, the amendments form part of the statute. Article 40(5) of the Vienna Convention on the Law of Treaties states: “Any State which becomes a party to the treaty after the coming into force of the amending agreement, shall, failing an expression of a different intention by that State: (a) be considered as a party to the treaty as amended...” Article 121(5) merely limits the ICC’s jurisdiction in relation to amendments with respect to state parties that have already accepted its jurisdiction.

Other commentators have also, correctly in the author’s view, argued that such interpretation is consistent with the purpose of Security Council referrals to expand the jurisdiction of the ICC (see D Akande, “Can the ICC Prosecute for Use of Chemical Weapons in Syria?”, EJIL: Talk!, 23 August 2013,

The slightly counter-intuitive nature of a non-state party being exposed to the jurisdiction of the ICC where a state party may not be is arguably alleviated by the fact that the latter remains subject to all other provisions of the Rome Statute.

Prosecution for supply of chemical weapons

Knowing supply of chemical precursors would likely fall within Art 25(3)(c), which refers to criminal responsibility of those who, for the purpose of facilitating the commission of a crime, aid, abet or otherwise assist in its commission, including providing the means for its commission. This is of particular significance in the context of the recent gassings of Syrian Kurds given the potential difficulty of identifying responsible members of ISIS.

It was reported that ISIS obtained chemical weapons from the Al Muthanna State complex in Iraq, the site of Saddam Hussein’s chemical weapons programme. Evidence previously gathered by the UN Monitoring, Verifi cations and Inspection Commission (UNMOVIC) concerning the supply of chemical weapons demonstrated that during the period from the mid-1970s to 1990 “over 200 foreign suppliers had provided major critical technology, equipment, items and materials that were directly used by Iraq for its chemical weapons… programmes… there were cases when suppliers were aware of the final use of the equipment and materials delivered to Iraq” (Compendium, Chapter VI: Iraq’s Procurement Activities at

Such prosecutions may prove too complex, necessarily involving consideration of whether foresight that chemical weapons supplied to the Iraqi government could or even would fall into the hands of an organisation such as ISIS would be sufficient to amount to aiding, abetting or otherwise assisting. But prosecutions of Westerners for aiding and abetting attacks perpetrated by the Syrian government to which chemicals were directly supplied (if proven to have been so perpetrated) would arguably be more straightforward.

In this regard, in his open letter to Vince Cable of 9 September 2013, Chair of the House of Commons Committees on Arms Export Control (CAEC), Sir John Stanley, wrote: “Syria has long been known to be a holder of chemical weapons and your Department were clearly fully aware that sodium fluoride and potassium fluoride are precursor chemicals in the manufacture of chemical weapons... Given that… do you agree on reflection that… these export licences should have been refused?”

It may be that the result of such further investigation as is conducted by CAEC ought to be placed before the Prosecutor for investigation within the terms of Art 25.

Author details: 
Sheryn Omeri

Sheryn is an Australian-born Iranian-Kurdish barrister practising at Cloisters. Previously, Sheryn worked as a solicitor-advocate at the Aboriginal Legal Service in Sydney, appearing for Aboriginal Australians before the criminal courts of New South Wales.