The Special Tribunal for the Crime of Aggression: Turning Commitment into an Operational Court Through Joint Action

Last month in Chisinau, 36 states and the European Union adopted the Enlarged Partial Agreement (EPA) that will govern the Special Tribunal for the Crime of Aggression against Ukraine (STCA). It is one of the three key documents along with the Agreement between Ukraine and the Council of Europe, and the Statute of the Tribunal.

The EPA now moves to domestic ratification to bring it into force, allow the Management Committee to be constituted, and open the tribunal's "skeleton phase", during which its operational structure will take shape in The Hague.

The idea of a special mechanism to hold Russia's senior political and military leadership accountable for starting a war in violation of the UN Charter emerged in 2022, shortly after the full-scale invasion of Ukraine by the Russian Federation. Given the limited jurisdiction of the International Criminal Court, the Special Tribunal is intended to fill the existing gap in international law and ensure accountability for the crime of aggression.

The path to establishing the Special Tribunal has been, and still is, challenging. The process has been accompanied by political and legal debates over the vision of this institution. Among the key challenges are: defining the crime of aggression; the legal status of the tribunal and its powers to hold accountable the so-called "Troika" (the president, the head of government, and the minister of foreign affairs), who as a general rule enjoy personal immunities protecting them from prosecution while in office; trials in absentia; and the relationship between the Special Tribunal and the ICC.

Certain countries (including some members of the G7) view the idea of a mechanism that could hold a state's leadership accountable for the unlawful use of force with caution, particularly given awareness that the prohibition on aggression could, in principle, apply to their own past uses of force. This reflects a broader politicisation of the prosecution of the crime of aggression — the same dynamic that explains why the ICC's own jurisdiction over the crime remains limited. A proposal to harmonise that jurisdiction with the Court's other core crimes was deferred at the July 2025 Special Session of the Assembly of States Parties to a further session in 2029, where states are now due to consider it.

To prove their support and give the Tribunal a real chance, the 36 states that adopted the EPA should stand by the undertaking through timely domestic ratification, commitment to the tribunal's budget, and sustained political backing through the phases ahead. The sooner ratifications are completed, the sooner the tribunal moves from framework to functioning institution.

To strengthen the tribunal's international legitimacy and its capacity, additional states can join the EPA. Ukraine continues to engage with countries across the globe, making the case that the STCA can serve the broader international community — establishing a modern precedent for prosecuting the crime of aggression that would not only advance international law, but also help deter future aggression. Strengthening that case also means showing tangible support for the international justice system as a whole, including the International Criminal Court and its jurisdiction over the crime of aggression — as Ukraine has already demonstrated and can be expected to continue.

Steps in support of the international justice system as a whole, including strengthening the ICC's jurisdiction over the crime of aggression, could help convince countries — among them a number of states of the so-called "Global South" — that have reservations about double standards, selective justice, and the narrow circle of potential suspects. Ukraine is already taking action in this direction, speaking out in support of enhancing the ICC's jurisdiction over the crime of aggression during the Special Session of the Assembly of States Parties in the summer of 2025 — and is expected to continue doing so.

The questions that will shape the tribunal

Meanwhile, tangible preparatory work is underway. The advance team, along with the states and institutions involved in the process, is working through the questions that will define how the tribunal operates — from financial and logistical aspects to trial structures, victim and witness engagement, protection measures, and more. Some of these issues are being actively addressed now. Others will fall to the Management Committee once constituted, and ultimately to the judges, who will resolve much of the remaining architecture through the rules of procedure and evidence.

Among these questions, several will require particular attention:

• Who will be recognised as a victim of the crime of aggression, and how will victims take part in the proceedings?
• How will engagement with witnesses be organised?
• How will cases be transferred and distributed between Ukrainian domestic proceedings and the tribunal?

These questions do not yet have definitive answers — and answering them well matters not only to ensure the tribunal is a meaningful instrument of justice, but also to provide clarity and shape realistic expectations for the millions of people affected by the war in different ways.

Although decisions on these matters will be made by the relevant institutions at later stages, a substantive and inclusive conversation about them should begin now. There are three reasons for this.

First, the complexity of these topics demands time and deep consideration. In the practice of international tribunals, for example, there is no ready-made solution that could simply be borrowed to define who qualifies as a victim of the crime of aggression. Approaches to the transfer and distribution of proceedings need to be developed and taken into account by prosecutors and investigators at the domestic level now, to prevent problems later. A considered discussion of these questions widens the range of possible solutions, and the recommendations it produces can feed into — and serve as a baseline for — the deliberations of the Management Committee and, later, the judges. Postponing the conversation does not make the answers any easier to find; on the contrary, it concentrates pressure at the moment of decision and risks delaying the entire process.

Second, involving a broader range of stakeholders — such as victims and civil society (non-governmental organisations, independent experts), who hold unique experience and knowledge — will substantively enrich the discussion. Survivor communities know what genuine, as opposed to merely formal, engagement in justice processes looks like. Civil society organisations have, since 2014, documented crimes, represented victims, and accompanied and strengthened justice processes both domestic and international. That knowledge can and should inform the tribunal's foundations.

Third, such engagement of victims and organisations shapes attitudes towards the tribunal and trust in it. It gives society in Ukraine and abroad the opportunity to understand the process better, raise concerns, and feel a sense of contribution to how the tribunal takes shape. Timely and meaningful involvement will help build support and trust in the Special Tribunal — support that can withstand moments of political turbulence in the future. Demonstrated public involvement and informed demand will also be visible to states weighing ratification or accession — a signal that those for whom the tribunal is being created are invested in its success.

The role of civil society

The STCA draws inspiration from the ICC in several respects, and civil society participation could be one more. Civil society organisations became the backbone of the International Criminal Court — strengthening its legal framework with their expertise, supporting victims through proceedings, and defending the institution through its hardest moments. Today, as the Court faces sanctions and unprecedented political pressure, it is often civil society actors who continue to stand by it at real risk to themselves. While constructive criticism is an integral part of civil society's work, its overall objective is to strengthen the institution and point out weaknesses that hinder the effective implementation of its mandate.

Ukrainian and international civil society can play a similar role for the STCA. These are organisations that document and investigate the very incidents the tribunal will address, that represent those who have suffered the most, and that carry practical experience from justice processes in Ukraine and other situations. Many participated in the creation of the international justice mechanisms that exist today.

Civil society organisations working internationally and in specific regions can also become advocates for the tribunal — supporting its financial stability, cooperation on arrest warrants, and other issues that will shape the STCA's de-facto legitimacy and relevance. That kind of involvement grows out of genuine engagement: organisations advocate for institutions they consider credible, responsive to the needs of those they represent, and open to their meaningful participation.

For that to happen, the consultations with civil society should be built into the tribunal's architecture — both formally and informally. This includes providing for civil society engagement in the rules of procedure of the Management Committee, alongside the informal channels of consultation and expertise that have served other institutions well.

Significant effort has gone towards making the STCA a reality. It is now a joint task for states, institutions, civil society and society broadly to ensure it becomes an effective instrument of justice for the crime of aggression.