Reports of the presumed use of chemical weapons — chlorine and more recently mustard gas — by Daesh (also know as the Islamic State) in Northern Iraq and Syria have appeared in the media for some time. A number of countries have reportedly gathered intelligence suggesting that Daesh is building up a capability to wage chemical war. On October 20, Reuters reported that the Organisation for the Prohibition of Chemical Weapons (OPCW) — the implementing agency of the Chemical Weapons Convention (CWC) — was sending a team to investigate one particular incident involving the alleged use of mustard gas in Northern Iraq.

The confirmation that Daesh has been using poison gas would signal a further escalation of the conflict and could mean a lowering of the threshold with regard to the international norm that prohibits the use chemical weapons. So what do we actually know? At this stage, we must rely on media reporting and statements from diplomatic and military sources, local officials, and doctors in hospitals that have treated victims of the alleged attacks. Also, reports have been published for some time indicating that Daesh has a keen interest in recruiting specialists with experience the manufacture and use of chemical weapons.

The information available in the public domain strongly suggests that improvised chemical weapons have indeed been used by Daesh. But assessments based on testimony and medical symptoms need to be confirmed by an independent investigation. In the case of mustard gas, there are good chances that this can be done. The agent and its characteristic degradation products and biomarkers can still be identified in environmental and biomedical samples several weeks or even months after an attack. In the case of chlorine, however, investigations are more complicated as there are no characteristic biomarkers or degradation products that would allow one to distinguish between a deliberate chlorine release and the natural background of chlorine in the environment. An investigation would have to rely on other techniques, including clinical examinations of survivors, post mortem examinations, epidemiological data, testimony of eyewitnesses, and an assessment of weapons remnants. The confidence in the investigation results may be lower, in particular if the investigation team arrives with some delay after the alleged incident, but it may nevertheless be possible to establish a strong case based on circumstantial and testimonial evidence.

This is why the investigation initiated by the OPCW is important. Such investigations apply internationally accepted standards of verifying the authenticity of evidence, ensuring an unbroken chain of custody, and evaluating the evidence including the results of analyses of samples taken from the locations of the alleged use and from victims, to demonstrate whether a chemical weapon has been used and what the circumstances of that use were. These investigations sometimes stop short of identifying the side responsible for the use of chemical weapons, but if the evidence available allows attributing responsibility, that finding becomes part of the investigation report.

In this context it is worth exploring what the implications would be if the OPCW investigation confirms that Daesh has used chemical weapons. Chemical weapons are internationally banned, but how relevant is international law in relation to an armed conflict involving a non-State actor such as Daesh? Some thoughts are below.

One could argue that international treaty law applying to the relationship between States does not come into play with regard to a use of chemical weapons by a terrorist organization. That does not mean, however, that the prohibition on the use of chemical weapons would not be relevant.

The prohibition on the use of chemical weapons is today considered to form part of customary international law. Daesh is a party to an armed conflict and the rules of customary international humanitarian law, including those on war crimes and individual responsibility, apply (see the explanation of rule 151 in the ICRC’s Handbook on Customary International Humanitarian Law). The ICRC also included the use of chemical weapons in its list of serious violations of international humanitarian law in non-international armed conflict (rule 156).

Furthermore, there are the provisions of the Rome Statute of the International Criminal Court (ICC). Even though it does not use the terminology of the CWC (“chemical weapons”), there is no doubt that the terms “employing poison or poisoned weapons” and “employing asphyxiating, poisonous or other gases, and all analogous liquid, materials or devices” found in the list of war crimes under the statute’s Article 8 would squarely apply to the use of chlorine or mustard gas as a weapon of war. Any such use would consequently come under the jurisdiction of the ICC.

Additionally, Daesh reportedly used chemical weapons on the territory of two States that are parties to the CWC, Iraq and Syria. Both States therefore have a right to request humanitarian and emergency assistance from the OPCW, under Article X of the CWC. At the same time, both countries are under an obligation to internalize the provisions of the CWC and apply its prohibitions to legal and natural persons that come under their jurisdiction. Irrespective of whether the two countries are actually able to enforce these prohibitions, any use of a chemical weapon by anyone on their territory would constitute a criminal act under their domestic laws.

Finally, States have the right to vest universal jurisdiction in their national courts over war crimes. A number of States have included the list of war crimes of the Rome Statute in their national legislation and claim universal jurisdiction for their courts to prosecute persons suspected of having committed such crimes (see the ICRC’s explanation of rule 157).

There is thus no doubt that any use of a chemical weapon by Daesh would constitute a violation of national laws and international law, including international criminal law. What does all this mean in practical terms? If the OPCW investigation confirms the use of chemical weapons by Daesh, several avenues would be available to the international community to respond:

  • The international community could invoke the provision of assistance to the victims of the use of chemical weapons found under Article X of the CWC, as well as under generally applicable rules and principles of international humanitarian law.
  • The Joint Investigation Mechanism for Syria, established by UN Security Council Resolution 2235 to identify those individuals, entities, groups, or governments responsible for any use of chemicals as weapons in Syria so that they can be held accountable could investigate the alleged uses of chemical weapons by Daesh (however, under its current mandate that would have to relate to confirmed uses in Syria).
  • The UN Security Council could request that the ICC initiate proceedings concerning these acts and individuals, leading to international prosecutions and convictions.
  • As States Parties of the CWC on whose territory the weapons were used, Iraq and Syria could seek national prosecutions of persons responsible for the attacks. So too could States that claim universal jurisdiction over serious war crimes.
  • States Parties of the CWC could also seek national prosecutions for individuals and organizations that have assisted, encouraged, or induced Daesh, in any way, to acquire and use chemical weapons.

While some of these measures may have little immediate effect, they should not be ignored. Successful convictions of war crimes can be enforced many years after the crimes have been committed. At the same time, organizations and individuals that have been providing assistance to Daesh for acquiring or using chemical weapons, in whatever form (financial, technical, by providing expertise, or in any other way), can be brought to justice. This would have a deterrent effect and also counter some of the propaganda Daesh uses to recruit new members.