Ralf Trapp recently wrote here about an investigation by the Organisation for the Prohibition of Chemical Weapons (OPCW) into the alleged use of chemical weapons in Northern Iraq and Syria by ISIL. Trapp said that if the allegations are proven, individual members of ISIL might one day wind up before the International Criminal Court (ICC). How might that happen, what might the charges be, and what kind of evidence would the prosecutors require?

Neither Iraq nor Syria are States Parties to the Rome Statute, which means that the ICC will have jurisdiction only if the UN Security Council refers the conflict to the ICC, as has occurred twice before with Sudan and Libya. To date, Russia and China have blocked a Syria ICC referral, though given the scale of the international crimes allegedly committed in Syria, it is hard to imagine that there will not one day be some form of accountability — at the ICC, an ad-hoc tribunal set up to adjudicate crimes from the Syria conflict, or national courts asserting jurisdiction. If the UNSC referred the conflict to the ICC, the prosecutors would investigate allegations of war crimes, crimes against humanity, and even genocide committed by any side in the conflict. In keeping with the approach of the UNSC referrals of Sudan and Libya to the ICC, a Syria referral would likely contain language excluding jurisdiction over nationals of non-States Parties aside from Syria with some involvement in the conflict, including the US and Russia. The UNSC would have to get creative in its drafting if it wished to confer jurisdiction only over certain nationals of non-States Parties who have joined ISIS, such as Iraqi fighters.

Regarding the use of chemical weapons, Trapp says that they are plainly criminalized by the Rome Statute’s prohibition on “poison or poisoned weapons” and “asphyxiating, poisonous or other gases, and all analogous liquid, materials or devices.” I think Trapp is right, but as Dapo Akande, Professor of Public International law at the University of Oxford, explains in this post, the argument is far from straightforward. Some, including Amal Clooney and Philippa Webb in this piece in the Journal of International Criminal Justice, contend that the quoted language does not apply to chemical weapons. The Rome Statute originally included a direct ban on chemical and biological weapons, but it was dropped at the same time as a ban on weapons causing unnecessary suffering was narrowed to apply only to those weapons listed in an annex (which does not exist because the States Parties never adopted one). This narrowing was done to avoid having the broader provision apply to nuclear weapons. The direct chemical and biological weapons prohibition was then dropped, apparently because some negotiators thought that there should be parity in approach to nuclear weapons (possessed by wealthy nations) and chemical and biological weapons (the more likely option for poorer countries). The claim that that the Statute therefore does not cover chemical and biological weapons was reinforced by Belgium’s efforts at the ICC Review Conference in Kampala in 2010 to amend the Statute to include a ban on chemical and biological weapons, indicating that there was an understanding among at least some States Parties that the Statute as written did not already do so.

But Akande persuasively argues (reinforcing what Trapp intuits) that the language in the Statute prohibiting poisonous and asphyxiating gases and analogous liquids, materials, and devices plainly applies on its own terms to most — if not all — chemical and biological weapons. Since the treaty text is clearly written, there is no need to consider the history of its drafting, per the Vienna Convention on the Law of the Treaties. In this case, the difficulty with relying on the negotiation history in the first instance is that it is highly indeterminate: Assessing what 120 countries “intended” when they adopted the Rome Statute is nearly impossible, and therefore the plain language of the treaty should govern when it is clear, as it is here.

To the extent chemical and biological weapons have been used against civilians, those responsible could also be prosecuted for the war crimes of intentionally targeting civilians or intentionally using force that will cause civilian loss of life clearly disproportionate to the anticipated military advantage, if the conflict is deemed to be international as well as non-international. They  may also be prosecuted for the crimes against humanity of murder, extermination, torture, or inhumane acts, if the attacks are committed in the context of a widespread or systematic attack on a civilian population. Of course the use of chemical and biological weapons would be just one of a long list of alleged criminal violations by ISIL that the ICC would investigate, if it were ever granted the jurisdiction to do so.

Finally, what kinds of evidence would be relevant to the ICC’s inquiry?

The OPCW investigation that Trapp describes — in addition to other forms of documentary, forensic, and witness evidence presently being collected — will be critical to any eventual investigation by the ICC or another tribunal into war crimes or crimes against humanity in Syria. Any accountability mechanism that one day assesses the crimes in Syria will be dependent on evidence collected now, in real time, which is why the work of OPCW and the Commission for International Justice and Accountability (for which, full disclosure, I am a board member), as well as other organizations collecting evidence that might otherwise be lost, is so essential. Further, there is generally a strong awareness among groups collecting evidence for the purpose of accountability that it must be done carefully and to a high standard. Many of these groups have either employed former investigators or have organized trainings to insure that they can meet the standards of a criminal trial, and evidence collection manuals are being devised to assist first responders to atrocity.

Although accountability in Syria for the use of chemical and biological weapons — as well as for the myriad other crimes occurring there — may be delayed because of the current absence of a mechanism to investigate and prosecute perpetrators, the collection and preservation of evidence today insures that the opportunity to obtain justice will not forever be lost.