On May 15, 2026, the Council of Europe finalized the Enlarged Partial Agreement establishing a Special Tribunal for the Crime of Aggression of the Russian Federation against Ukraine. Thirty-six countries and the European Union have stated their intention to join the agreement.
This is an important step toward accountability for Russia’s war against Ukraine. At the same time, international law distinguishes among several categories of the gravest international crimes: the crime of aggression, war crimes, crimes against humanity, and genocide.
We have prepared answers to key questions about why a Special Tribunal is needed, whom it may concern, how it differs from the International Criminal Court (ICC), and why it matters for Ukraine and the international legal order.
1. What is the crime of aggression, and why is it a separate international crime?
Under international law, the crime of aggression concerns the planning, preparation, initiation, or execution of an act of armed aggression that violates the UN Charter and attacks the sovereignty, territorial integrity, or political independence of another state.
In the context of Russia’s current war, this refers to the Russian Federation’s armed aggression against Ukraine and its assault on international peace and security.
The crime of aggression is recognized as one of the gravest international crimes because it concerns the unlawful use of force itself — the decision to wage war in violation of peace, security, and international law.
2. What makes the crime of aggression difficult to prove?
It is not enough to establish that an armed attack took place. Prosecutors must show that a specific individual was in a position to effectively control or direct a state’s political or military action, and that this person made, shaped, or implemented the decision to commit aggression.
The act of aggression must also constitute a manifest violation of the UN Charter.
This means investigators must reconstruct decision-making at the highest levels of government — a process that is especially difficult because direct written orders often do not exist.
3. What is the Special Tribunal for the Crime of Aggression against Ukraine?
The Special Tribunal is an international judicial mechanism created to address the crime of aggression committed by the Russian Federation against Ukraine. Its purpose is to hold accountable senior political and military leaders involved in decisions to launch and conduct Russia’s aggressive war. This is why the crime of aggression is often called a “leadership crime.”
The Tribunal’s mandate is to establish the facts, examine evidence, determine the individual criminal responsibility of specific officials, and close the jurisdictional gap that currently prevents the ICC from prosecuting Russia’s crime of aggression against Ukraine.
The Tribunal will be established within the framework of the Council of Europe, in cooperation with Ukraine, and funded by a group of states supporting the initiative. This group may include countries that are not members of the Council of Europe.
4. Why is a Special Tribunal needed to prosecute the crime of aggression?
A separate tribunal is necessary because of legal limitations that prevent the ICC from fully exercising jurisdiction over Russia’s crime of aggression against Ukraine.
For that reason, the international community has developed a special mechanism to close this gap and ensure accountability for the decision to start the war itself.
5. Who could be held accountable by the Tribunal, and why does individual responsibility matter?
The Special Tribunal will focus on individual criminal responsibility. Unlike some other international judicial or quasi-judicial bodies, it will not be designed to award reparations. Its purpose will be criminal accountability, including the possibility of imprisonment.
Those potentially responsible for the crime of aggression include members of Russia’s senior political and military leadership who took part in decisions to plan, prepare, initiate, or execute the armed aggression against Ukraine. This may include, for example, a head of state or government, a minister of defense, a minister of foreign affairs, or other senior decision-makers.
At the same time, several issues may complicate the prosecution or sentencing of such individuals. These include the existence of official immunities for certain sitting officials — in particular, heads of state, heads of government, and ministers of foreign affairs — as well as the broader challenge of securing the physical presence of suspects or accused persons before the court.
For such situations, the Tribunal’s Statute provides for the possibility of pursuing justice after the relevant officials leave office or otherwise lose immunity. It also allows for investigation and trial in absentia, meaning proceedings may take place even if the accused person is not physically present in court.
Individual responsibility matters because it moves accountability beyond the abstract responsibility of the state. It identifies the people who made or carried out decisions leading to aggression. This prevents responsibility from being dissolved into collective blame and creates real personal consequences for those who chose to wage an illegal war.
6. How is the Special Tribunal connected to the ICC?
The ICC remains the central institution in the system of international criminal justice. The Special Tribunal is intended to complement the ICC’s work, not replace it.
After the Tribunal is established, it is expected to conclude a cooperation agreement with the ICC. This mechanism should help coordinate action, support effective information-sharing, and avoid duplication of proceedings.
If a relevant person is arrested on the basis of an ICC request, proceedings before the ICC will have priority over proceedings before the Special Tribunal. This confirms the ICC’s leading role and defines the Tribunal as an additional instrument of international accountability.
7. How is the crime of aggression different from other international crimes?
- The crime of aggression and war crimes
The crime of aggression concerns the decision to start a war. It is a crime of senior state leadership — those who ordered or directed the attack.
War crimes concern how the war is conducted: the killing of civilians, torture, attacks on hospitals, abuse of prisoners of war, and other serious violations of the laws and customs of war. War crimes can be committed by a wide range of actors, from soldiers to generals.
- The crime of aggression and crimes against humanity
Crimes against humanity involve a widespread or systematic attack against a civilian population. They may include murder, persecution, deportation, enforced disappearance, and other grave abuses. They can occur in peacetime or during war and may be committed by a broad range of perpetrators.
The crime of aggression, by contrast, is an interstate act. It concerns the unlawful armed attack by one state against another, rather than the treatment of civilians as such.
- The crime of aggression and genocide
Genocide is the most specific of the core international crimes. It is not enough to prove mass killing or widespread violence. Prosecutors must establish special intent: the intent to destroy, in whole or in part, a protected group as such — on national, ethnic, racial, or religious grounds.
The crime of aggression does not require this special intent. To qualify as aggression, it is enough to establish the unlawful armed attack by one state against another, provided the legal threshold is met.
Cases concerning the planning or commission of genocide may be heard by the ICC, as well as by national courts, where jurisdiction exists and sufficient evidence is available.
At the same time, effective investigation and prosecution of this crime in Ukraine requires changes to national legislation. Read more here.
8. Will the Special Tribunal examine allegations of genocide?
No. The Special Tribunal will have a clearly defined jurisdiction limited to the crime of aggression. It will not examine other international crimes.
9. Can Russia’s crimes against culture serve as evidence in cases concerning aggression or genocide?
In brief: in a case concerning aggression, probably not. In a case concerning genocide, yes — but with important legal qualifications.
The crime of aggression concerns, first and foremost, the decision to start a war. It focuses on the actions of senior political and military leaders who plan, prepare, initiate, or execute an act of aggression. For that reason, crimes against culture — Russification, bans on the Ukrainian language, destruction of cultural heritage, or the imposition of an occupation identity — are not central to proving the crime of aggression itself.
In such proceedings, the Tribunal would primarily examine decisions by Russian leadership to launch and conduct an aggressive war, rather than cultural policies in occupied territories.
In a genocide case, however, the situation is different. The most difficult element to prove is often special intent: the intent to destroy a protected group as such, in whole or in part. In this context, crimes against culture may have significant evidentiary value.
This includes practices aimed at destroying the identity of a community: forced Russification, language bans, persecution of cultural figures, destruction of monuments, and attacks on educational and religious institutions. The forced transfer of children from one group to another is especially significant. In international law, it is directly connected to genocide, and it also echoes Raphael Lemkin’s original thinking on “cultural genocide.”
Crimes against culture, standing alone, are not always sufficient to prove genocide. But taken together with other evidence, they may help demonstrate an intent to destroy a group not only physically, but also as a distinct community — with its own language, memory, history, and identity. This was precisely the kind of destruction emphasized by Raphael Lemkin, the jurist who coined the term “genocide.”
International practice has already recognized the relevance of such evidence. It has been considered, for example, in proceedings before the International Criminal Tribunal for the former Yugoslavia, the International Criminal Tribunal for Rwanda, and in the work of Canada’s Truth and Reconciliation Commission.
10. Why do the Tribunal and genocide investigations matter for Ukraine and the international order?
They are necessary to show that aggressive war and the gravest international crimes cannot go unpunished. Violations of international law must have legal consequences for those who make decisions, organize crimes, or carry them out.
For Ukraine, this is not only a matter of punishing perpetrators. It is also about establishing the truth, protecting victims and survivors, and preventing such crimes from happening again.