Case Explained: Negotiating a Treaty on Crimes Against Humanity – Introduction to the Joint Symposium – Legal Perspective

This article is cross-posted on EJIL: Talk!

We are delighted to host this symposium and grateful to the editors of Just Security and EJILTalk! for publishing it.

Over the coming days, the two sites will publish expert contributions leading into the negotiations of the draft International Convention on the Prevention and Punishment of Crimes Against Humanity (CAH). These negotiations will take place at the United Nations in New York from Jan. 19-30.

The negotiations have the potential to fill significant legal and institutional gaps. CAH are among the most serious crimes of concern to the international community. Yet, unlike other serious international crimes (such as war crimes and genocide) they are not covered by a specific international convention. This legal gap limits coordinated global action to prevent such atrocities, prosecute perpetrators, and assist victims. The draft Convention defines and prohibits these crimes, requires States to criminalize and prevent them, and enhances international cooperation, including by extradition and mutual legal assistance.

This symposium builds on an event we organized at the margin of the 69th meeting of the Committee of Legal Advisers on Public International Law (CHADI) at the Council of Europe in Strasbourg. The essays in this series – by Judge Guénaël Mettraux, Prof. Leila Sadat, Prof. Sean Murphy, Dr. Stephanie Egerer-Uhric and Dr. Jorg Polakiewicz – are intended to offer useful insights to negotiators on outstanding substantive issues and challenges that may arise from the negotiation process, with the aim of contributing to the further strengthening of the draft.

Why We Need a CAH Convention

In his forthcoming contribution, Judge Mettraux explains that the concept of CAH was first used as a lay concept in 1748. The concept has since crystallized as a separate category of international crime during WWII and was further refined in the jurisprudence of international criminal tribunals since Nuremberg. Yet, CAHs have not been codified in a dedicated CAH Convention. Doing so is essential for several reasons.

First, a CAH Convention will fill critical gaps in the existing legal framework by addressing criminal conduct that is not adequately captured by the current treaty regime. Rather than being duplicative of existing conventions, a CAH Convention would serve distinctive and complementary prosecutorial functions. Of the generally recognized core-crimes, war crimes are codified in the Geneva Conventions and require a nexus to armed conflict and genocide under the Genocide Convention requires proof of specific intent to destroy a protected group. CAHs, however, encompass a broader category of conduct. They address widespread or systematic attacks directed against civilian populations, without the demanding mens rea threshold required for genocide. A CAH Convention would therefore address violations that fall outside the scope of war crimes and genocide, including discriminatory and other inhumane acts committed in peacetime, regardless of the nationality of victims or perpetrators. It would broaden the scope of the conduct that is regarded as criminal under international law and strengthen – rather than duplicate – the existing international criminal framework by filling existing normative gaps. This issue is discussed in several contributions, including that of Dr. Polakiewicz.

Second, a dedicated CAH Convention will also fill significant gaps that remain in the international legal framework created by the International Criminal Court (ICC), notwithstanding its jurisdiction over CAH. As Prof. Sadat’s contribution will discuss, the ICC Statute does not include an enforceable obligation by States to prevent CAHs, and does not provide for State responsibility, as it focuses only on individual criminal responsibility. Further, the ICC Statute also lacks specific provisions on mutual legal assistance and inter-State cooperation, which are now standard provisions in modern international criminal law treaties. In addition, the ICC complementarity regime places prosecutorial responsibility primarily on domestic criminal systems. However, practice has shown that the limited jurisdiction of the ICC as well as its limited resources and structural constraints have resulted in a very limited docket. By addressing these gaps, a dedicated CAH Convention would strengthen the international legal order and provide States with the necessary normative and operational tools related to CAH.

Third, and finally, a CAH Convention would complement existing domestic tools. In her contribution, Dr. Egerer-Uhrig will highlight the importance of a dedicated CAH Convention based on her experience as a prosecutor in Germany. Her two decades of investigative and prosecutorial practice, especially on crimes committed in Syria, show that CAH can be effectively prosecuted domestically, but also that no two conflicts are alike and that effective international cooperation is indispensable. Cooperation with international partners is essential in every stage of the prosecution of CAH, from evidence gathering to extradition and mutual legal assistance. By establishing a framework of cooperation, the adoption of a CAH Convention would constitute a fundamental and visible step towards preventing and punishing CAH.

Can We Strengthen the ILC Draft?

The draft Convention under discussion was developed and finalized by the International Law Commission (ILC) in 2019, following numerous years of deliberation. Professor Murphy served as the Special Rapporteur for the project and his contribution will describe well the draft, its conceptual structure, and its content. In 2024, after extensive negotiations, the U.N. General Assembly (UNGA) agreed to initiate an intergovernmental negotiating process – scheduled to begin in January 2026.

The ILC Draft is an excellent basis for the new Convention. It reflects the thinking and deep discussions of globally representative groups of eminent lawyers bringing together not only legal expertise but also different perspectives as to what is needed and what is possible. As drafted, the CAH Convention is already a significant step forward.

However, as noted by Prof. Sadat, to reach consensus and initiate negotiations, significant compromise was made at UNGA. Several proposals are on the table to further strengthen the draft.

The first issue is a definitional one. Article 2 of the draft defines CAH as certain defined acts “when committed as part of a widespread or systematic attack directed against any civilian population, with knowledge of the attack.” This definition mirrors Article 7 of the Rome Statute. There are benefits, including a coherent interpretation, in having a consistent definition that is also the distillation of the practice of prior jurisprudence. Moreover, nothing in the draft precludes States to adopt a broader definition in their domestic system. That said, as the understanding of the CAH and some of its aspects has progressed since the adoption of the Rome Statute, some have called for the inclusion of different or additional elements, for example new conduct such environmental destruction, gender apartheid, forced marriage, slave trade and starvation. There have also been proposals suggesting the addition of a Martens Clause or advancing more specifically children’s rights, gender issues, and disability rights. The critical question is whether the inclusion of additional elements would allow for the prosecution of acts that are not yet covered by Art. 7(1)(k) of the Rome Statute, whether it would create additional expectations that cannot be fulfilled, and whether it would really facilitate the prosecution of CAH. Moreover, agreement on the Convention might become more difficult if the carefully negotiated and broadly agreed definition of the crime would to be amended.

A further issue is whether a new CAH Convention should contain explicit provisions excluding functional and personal immunities. Recent developments in international law, including at the ICC and the ILC, support the exclusion of immunity in CAH cases. At the same time, however, it is important to consider carefully how immunities should be addressed in a treaty that regulates inter-State obligations rather than individual international criminal responsibility. In domestic proceedings, national legislation would likely remain bound to respect the personal immunities of incumbent foreign “troika” (president, foreign minister, prime minister). Differently, and consistent with the most recent ILC draft articles, functional immunity might not apply. However, the draft faced some significant opposition when it was discussed (see also comments here) so reopening the debate may make CAH negotiations more difficult.

Finally, there are important questions of treaty design, for example on issues of reservations and other final clauses. Importantly, moreover, the dispute settlement clause (Article 15) raises significant questions and should be clarified. In particular, should parties agree to compulsory jurisdiction by the International Court of Justice (ICJ) over disputes between State Parties, or should the existing (and unclear) opt-out mechanism be retained? Limiting the ICJ’s jurisdiction would clearly limit the effectiveness of the Convention. The experience of the dispute resolution clause of the Genocide Conventions shows that access to the ICJ can serve as a powerful mechanism to address non-compliance, including (as shown in The Gambia v. Myanmar and South Africa v. Israel) in unexpected ways. The institutional role and jurisprudence of the ICJ have demonstrated that it is well placed to adjudicate such kinds of cases, always in accordance with the highest standards of judicial independence and intellectual rigor.

Are There Procedural Challenges?

As part of the compromise, the negotiation process that begins in January will be protracted: a second Preparatory Committee meeting (Prep-Com) is scheduled for April 2027, which will be followed by two Diplomatic Conferences scheduled for 2028 and 2029. It will be important that the two years are used in a meaningful way to strengthen the draft. It might be difficult to keep momentum for the four years’ process, knowing that the real decisions will only be taken in 2029. Innovative and sustained efforts will be key.

Another critical element will be whether the Prep-Com and Diplomatic Conference will take decisions by voting, as it is normal within the U.N. system, or would rather try to work by consensus (following the UNGA 6th Committee model). While consensus would be theoretically preferable, an obligation to reach consensus would make it difficult to agree on a robust outcome and would result in, if any, a much-diluted draft. Furthermore, the option of voting as a last resort is generally considered an essential tool for achieving consensus.

Finally, the process will clearly benefit from the expertise and knowledge of civil society organizations (CSOs). This is also important for transparency and inclusivity reasons, also because CSOs can strengthen the negotiation process. CSOs accredited to the Economic and Social Council (ECOSOC) will participate in both Prep-Com and the Diplomatic Conference, it will be important that, at the end of the 2026 Pre-Com, delegates decide to allow for the participation also of non-ECOSOC accredited organizations and other stakeholders, be it as part of the formal negotiations or through other means.

Conclusion

Crimes against humanity are some of the most serious international crimes. The forthcoming negotiations of a dedicated Convention can fill a significant legal and institutional gap. It will be key to use this opportunity to develop a strong and coherent draft that advances international law, to the benefit of humanity. We hope the symposium will help negotiators achieve these important goals.

FEATURED IMAGE: Gavel in front of a globe (via Getty Images)