Twelve Years On: An Exceptional Chemical Weapons Tribunal

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It is almost two years since a Permanent Member of the UN Security Council unilaterally decided to wage war against an independent European state. What response might we have expected in that time? More particularly, how might we have expected the international community to respond?

Now let’s imagine we are a decade on. Twelve long years of war. The war has caused at least 500,000 deaths (basically the entire population of the Hague). Murder, rape, forced disappearances and torture against civilian populations are widespread and systematic. In some cases, chemical weapons have been used against civilian populations. Yet there are so many atrocities that the dead, the tortured, the internally displaced, the refugees, the damage to homes and property are registered by the world at large as updated statistics that start to lose significance. Global donor fatigue has set in. The international community is becoming inured to the constant stream of reports of war crimes and atrocities. We’ve repeated the lamentations so often, we get tired, we weaken our resolve, we’ve tried what we can, it’s all just too hard. Other conflicts, issues and crises are now in the headlines.

This projection is more than an imagined bleak future. This is the situation in Syria.

In this context of intensifying neglect of the Syrian conflict, it was positive to read about an initiative to create a new tribunal for Syrian atrocities recently launched in the Hague. On 30 November 2023, a group of Syrian rights organizations and individuals issued a Declaration calling on states to establish an Exceptional Chemical Weapons Tribunal. The Declaration was made following two years of consultations with diplomats and Ministers of 44 governments, international organizations and legal experts.

On the same day, at the 28th session of the Conference of States Parties to the Chemical Weapons Convention, the Conference adopted a decision recommending collective measures by states parties. States parties were called on ‘to afford the greatest measure of assistance possible in connection with criminal investigations or criminal proceedings in accordance with international law relating to chemical weapons attacks in the Syrian Arab Republic, and to provide appropriate support to relevant national and international accountability efforts’. The decision also urged ‘the General Assembly and the Security Council to take appropriate actions to address the situation and advance accountability’. This was the first time Article XII, paragraph 3 of the OPCW Convention had been invoked, empowering the Conference to recommend collective measures to states parties.

The initiative to create a tribunal is more than timely, it is overdue. Comparative attention given to avenues for prosecution of international crimes committed in Ukraine is stark. In the two years since Russia’s invasion of Ukraine, governments and legal experts have not only debated but deployed mechanisms for the prosecution of international crimes committed in the course of the Russia/Ukraine conflict. Four days after Russia’s invasion, on 28 March 2022, the ICC Prosecutor announced he would seek authorization to open an investigation into the situation. Two days later, on 2 March 2022, 39 states parties issued a joint referral, enabling the Prosecutor to expedite the matter and proceed straight to an investigation. A year later, on 17 March 2023, an arrest warrant was issued against the President of the Russian Federation and his Commissioner for Children’s Rights. On 2 February 2023, the European Union announced the establishment of an International Centre for the Prosecution of the Crime of Aggression against Ukraine to coordinate the collection of evidence and support national investigations into the crime of aggression related to the war in Ukraine. Debate and discussion continue between states, international organizations, civil society and academics regarding the establishment of a Special Tribunal for Aggression, an initiative that has already garnered the support of over 20 states, the EU, NATO, the Council of Europe and the OSCE. 

International lawyers need to engage with the Syrian initiative with the same level of intellectual energy devoted to other contexts. This post provides a preliminary assessment of some of the legal challenges involved.

Is there a need for another international criminal tribunal?

To date, the Syrian conflict has largely been a site of impunity. Most avenues to justice are blocked for victims and survivors of international crimes in Syria. Unlike Ukraine, where the Prosecutor General is currently investigating 80,000 cases, there is no prospect of perpetrators being tried within domestic courts in Syria. Similarly, unlike the situation in Ukraine, the International Criminal Court does not have jurisdiction to prosecute crimes committed in Syria. As Syria is not a party to the Rome Statute of the International Criminal Court, the ICC is unavailable to prosecute crimes committed in Syrian territory by Syrian nationals and could only claim jurisdiction in the event of a Security Council referral. Russia and China vetoed referral of the situation to the ICC in 2014.

In these circumstances, the only currently available accountability mechanism for international crimes committed in Syria is the exercise of universal jurisdiction by third party states. States including Austria, France, Germany, Sweden, Switzerland and the Netherlands are engaged in investigations and trials in relation to international crimes committed in Syria. In the case of France, Germany and Sweden, this includes potential prosecution of individuals alleged to have committed the crime of chemical weapons use. In the case of France, last month in November 2023, French judges issued an arrest warrant for President al-Assad, including for alleged complicity in the August 2013 chemical weapons attacks in the city of Douma and the district of Eastern Ghouta.

The level, complexity and political sensitivity of these proposed prosecutions reflects the importance of ensuring their international legitimacy. While universal jurisdiction exercised by domestic courts is a valuable mechanism to fill enforcement gaps in international criminal law, its use should be circumscribed where it is possible to rely on courts with a greater nexus to the crime or a greater claim to representation of the relevant communities. An international criminal tribunal established at the request of the victims set up by a representative group of states, with the support of states from the region and non-Western states, would be better equipped to coordinate prosecution of these crimes and fulfil the objectives of international criminal law.

Does the use of chemical weapons attract individual criminal responsibility?

Few treaty drafting disputes are better known than the decision to remove the crime of the use of nuclear, chemical and biological weapons from the initial draft of the Rome Statute of the International Criminal Court. According to William Schabas, this was done on the basis that certain states objected to the inclusion of the use of nuclear weapons, while non-nuclear weapons states felt the exclusion of nuclear weapons alone ‘smacked of hypocrisy’ (chemical weapons being regarded as the ‘poor man’s’ nuclear weapon). Forty-five states have since ratified a 2010 amendment to the Rome Statute recognizing the International Criminal Court’s jurisdiction over serious violations in non-international armed conflicts, including (xiii) employing poison or poisoned weapons; and (xiv) employing asphyxiating, poisonous or other gases, and all analogous liquids, materials or devices. Yet there is ongoing debate as to whether the Rome Statute encompasses the crime of chemical weapons use (see, for example, scholarly contributions by Amal Alamuddin and Philippa Webb; Dapo Akande; Ralf Trapp; Alex Whiting; and Kevin Heller).

The fact that states declined to vest jurisdiction in the ICC for the explicit crime of chemical weapons use does not impact the position under general international law. Under both treaty and customary international law, the use of chemical weapons is recognized as a crime attracting individual criminal responsibility. This extends to the use of chemical weapons in non-international armed conflicts. According to the combined effect of Article 1 and Article VII of the Chemical Weapons Convention, states parties (including Syria, who acceded to the Convention in 2013) agree to enact penal legislation prohibiting ‘natural and legal persons’ from using chemical weapons in any circumstances, including non-international armed conflicts.

These treaty provisions confirm the position under customary international law. The use of chemical weapons in non-international armed conflicts is widely accepted as prohibited under customary international law (Rule 74, ICRC Study on Customary International Humanitarian Law and see associated state practice in Volume II of the Study). In the Tadić case, the International Criminal Tribunal for the Former Yugoslavia held that ‘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’ (Decision in Interlocutory Appeal on Jurisdiction, 2 October 1995, para 124). Under customary international law, serious violations of international humanitarian law are war crimes, which attract individual criminal responsibility, including in relation to those committed in non-international armed conflicts (Rules 151 and 156, ICRC Study on Customary International Humanitarian Law). In its Commentary to Rule 156, the ICRC Study notes that the use of prohibited weapons, including chemical weapons, in non-international armed conflicts would constitute a war crime (at pp 599-600).

Can states vest an international tribunal with jurisdiction to prosecute the crime of chemical weapons use?

 The legal routes through which jurisdiction can be vested in international tribunals are various. While jurisdiction is commonly imagined as an aspect of state sovereignty, it can also be an obligation owed to individuals and a dimension of a state’s engagement with the international community. Here, I propose three possible options for vesting jurisdiction in the Exceptional Chemical Weapons Tribunal, derived from three different sources of authority that could be relied on cumulatively or independently. The choice of jurisdictional basis may have implications for the extent of the tribunal’s authority, including its capacity to override the immunity of Syrian state officials.

  1. Delegation of state jurisdiction

Following the trend established by the Nuremberg tribunal, it is accepted that – in jurisdictional terms – states can do together ‘what any one of them might have done singly’. Under this approach, states are able to ‘pool’ their individual legal authority to prosecute and delegate this jurisdiction to an international tribunal. International tribunals are thereby bounded within the jurisdictional limits on those states delegating the jurisdiction.

It is therefore relevant to inquire into the scope and limitations on the jurisdictional authority of states in this context. Under Article VII(1)(a) and (c) of the Chemical Weapons Convention, states agree to criminalize chemical weapons use on their territory (or in any place under their jurisdiction) and by their nationals. The 1990 travaux preparatoires of the Convention reflect that there was controversy at the time over the extent to which states parties were able and/or willing to recognize extra-territorial jurisdiction with respect to their nationals abroad (p188).

The fact that even nationality jurisdiction was controversial for certain states reflects that the Convention was drafted at a time when extraterritorial prosecutions were less common, exhibiting a reluctance that has since been overtaken by other tendencies. The scope of obligations agreed to under the Convention does not limit the broader right of states to exercise jurisdiction outside the Convention context. It is now well accepted in customary international law that states may claim jurisdiction over crimes committed on their territory or by their nationals (‘territoriality’ or ‘nationality’ jurisdiction). States may also claim jurisdiction where their nationals have been victims of a crime (‘passive personality’ jurisdiction) or their fundamental state interests are threatened (‘protective’ jurisdiction). While some may argue that a state also possesses universal jurisdiction which can be delegated to the tribunal, I will address this under the heading below of ‘international jurisdiction’.

Syria is unlikely to delegate its territorial or nationality jurisdiction to the tribunal. In these circumstances, one option is for states establishing the tribunal to invoke their protective jurisdiction on the basis that deterrence of the use of chemical weapons is vital to their national security interests. The related legal basis of self-defence has been used by the US, the UK and France to justify strikes against chemical production and storage facilities in Syria. If states are willing to rely on this justification to use force, it could also serve as the basis for a claim to jurisdiction in the establishment of a tribunal.

  1. Victims’ right of access to justice

The exercise of jurisdiction is more than a question of state right. As Alex Mills identifies, ‘jurisdiction is no longer exclusively a right of states, but is at least to some extent a matter of individual right, that is, an obligation owed to individuals’. It is significant that the tribunal has been called for pursuant to a Declaration by victim associations, victims and their families. Numerous human rights conventions recognize that states parties are required to provide individuals whose rights and freedoms have been violated to an effective remedy (see, for example, Article 2(3) of the International Covenant on Civil and Political Rights). This extends to an obligation to prosecute perpetrators of international crimes. On 16 December 2005, the General Assembly passed Resolution 60/147 on the ‘Basic Principles and Guidelines on the Right to a Remedy and Reparation for Victims of Gross Violations of International Human Rights Law and Serious Violations of International Humanitarian Law’. According to this resolution, ‘States have the duty to investigate, and if there is sufficient evidence, the duty to submit to prosecution the person allegedly responsible for [gross violations of international human rights law and international humanitarian law]’ (para 4). The establishment of a tribunal could be justified on the basis of satisfaction of the rights of victims to an effective remedy.

  1. International jurisdiction

In the prosecution of certain crimes, it is increasingly clear that jurisdiction does not always find its source exclusively in state sovereignty. Normatively, in relation to international crimes, it makes more sense to recognize a form of international jurisdiction (or ‘universal jurisdiction’) exercised, not on behalf of individual states, but on behalf of the international community. International crimes, distinguishable from transnational crimes or domestic crimes, are identifiable based on an overwhelming consensus in the international community as to their moral heinousness. According to this characterization, universal jurisdiction is a strategy devised by the inter-state community to address international criminal law’s enforcement gaps. Where there is recognized international consensus to exercise jurisdiction over certain heinous crimes, any state or group of states may vest universal jurisdiction in their domestic courts or indeed in an international tribunal.

It is clear that international consensus exists on the right to exercise universal jurisdiction over the crime of chemical weapons use in Syria. Universal jurisdiction exists under customary international law in relation to war crimes in international and non-international armed conflicts, as recognized in Rule 157 of the ICRC Study on Customary International Humanitarian Law. Further evidence of this consensus can be inferred from the General Assembly’s agreement to establish the International, Impartial and Independent Mechanism to Assist in the Investigation and Prosecution of Persons Responsible for the Most Serious Crimes under International Law Committed in the Syrian Arab Republic since March 2011 (the ‘IIIM’). Through the establishment of this body, the international community has effectively recognized jurisdiction to investigate and prosecute the crime of chemical weapons use in Syria. In the UN Secretary-General’s report to the General Assembly, the IIIM was recognized to have a ‘quasi-prosecutorial function’ with ‘an explicit nexus to criminal investigations, prosecutions, proceedings and trials’ (para 32). On 27 June 2018, the Conference of States Parties of the OPCW adopted a decision in which it reaffirmed that those responsible for the use of chemical weapons should be held accountable and decided that the Secretariat would ‘preserve and provide information’ to the IIIM. The head of the IIIM Catherine Marchi Uhel has confirmed she is ready to work with a new court and that ‘[a]n international body with dedicated resources and a team that has developed expertise on building cases around chemical weapons incidents might be well placed to deal with these types of cases’.


The aim of this post is to recognize that those responsible for chemical weapons use in Syria have so far been granted impunity by the international community in relation to a recognized international crime in circumstances where there is a right – and arguably a duty – to exercise jurisdiction. Significant relevant evidence relating to these crimes has already been collected by the IIIM. The Declaration by victims and victims organizations of chemical weapons attacks in Syria calling for the establishment of a tribunal demands the attention of international legal scholars to instruct on its legal potential. Ultimately, the establishment of an Exceptional Chemical Weapons Tribunal will depend on state will. Yet where there is a way, there must be a will. After twelve years of atrocity, to determine otherwise is to be complicit in impunity.

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Nicolas Boeglin says

December 11, 2023

Dear Professor Hovell

Many thanks for this extremely interesting post.

With regards to the status of the Convention officially entittled "Convention on the Prohibition of the Development, Production, Stockpiling and Use of Chemical Weapons and on their Destruction" that entered into force in 1997, I have a question: there are 193 States Parties to this convention, with one singular exception: Israel.


In your view (or of some of our EJIL Talk colleagues and their contacts at IDF International Law Dept in Israel), any explanation known or made public of such "israeli exceptionalism" among the international community?

Sincerely yours

Nicolas Boeglin