The crime of aggression stands as one of the most serious breaches of international law, representing a fundamental violation of the sovereignty and territorial integrity of States. The Russian Federation’s invasion of Ukraine constitutes a continuing crime of aggression and represents a continuous pattern of unlawful use of force, from the 2014 occupation of Crimea and military intervention in Donbas to the full-scale invasion that commenced on Feb. 24, 2022, which continues to the present.
Building On the Model Indictment
Just months after the Russian Federation’s full-scale invasion of Ukraine in February 2022, Open Society Justice Initiative (OSJI) published a Model Indictment for the Crime of Aggression Committed against Ukraine. That document demonstrated the abundant publicly-available evidence supporting prosecution of senior Russian officials for the crime of aggression, as well as the feasibility of indictment in appropriate jurisdictions.
Three years on, OSJI has now published an updated Memorandum for Prosecution of the Crime of Aggression Committed Against Ukraine. Building upon the 2022 Model Indictment, the Memorandum provides additional information and analysis of use to international and national prosecutors with responsibility for investigating and prosecuting the crime of aggression in Ukraine.
The Memorandum covers a broader time period to better analyze, and take account of the full scale of progressively-expanding and intensifying aggression committed by the Russian Federation against Ukraine in three phases: (1) the occupation of Crimea beginning in February 2014, (2) the intervention in Donbas from April 2014, and (3) the full-scale invasion initiated in February 2022, which continues to this day. By tracing an unambiguous, unbroken pattern of aggression over more than a decade, this Memorandum highlights that the violation of Ukraine’s sovereignty and territorial integrity is not a past offense, but an ongoing breach of one of the most foundational norms of international law.
It details how specific individuals contributed to Russia’s acts of aggression, including through their use of UN Security Council meetings and other high-level forums to justify and legitimize unlawful actions already undertaken. These individuals prepared for aggression by establishing false justifications, amassing troops, and engineering incidents as pretexts; initiated aggression through declarations of hostilities and the first use of force; and executed these acts by commanding armed forces and governing occupied territories. Through these actions, they bear individual criminal responsibility for committing the crime of aggression under international law.
Significantly, the Memorandum for Prosecution also addresses Belarus’s role in facilitating Russia’s unlawful use of force. It outlines how Belarus, under President Alexander Lukashenko, has provided critical support for the Russian invasion by allowing the use of its territory for troop deployments, missile launches, and other logistical operations. It is evident that Belarus’s actions amount to knowledge and substantial assistance in the commission of the crime of aggression. As such, Lukashenko and other senior Belarusian officials may be individually criminally responsible for “action of a State in allowing its territory, which it has placed at the disposal of another State, to be used by that other State for perpetrating an act of aggression against a third State.”
Efforts to Investigate the Crime of Aggression
The Memorandum for Prosecution adopts the definition of aggression under international criminal law as set out in Article 8 bis of the Rome Statute of the International Criminal Court (ICC). Despite Ukraine’s recent ratification of the Rome Statute, the ICC lacks jurisdiction over the crime of aggression in Ukraine because of the jurisdictional rules governing that crime. Ukrainian prosecutors are pursuing the crime of aggression against Russia through domestic investigations, but this has often focused on low-level perpetrators.
Most significantly, in June 2025, Ukraine and the Council of Europe formally adopted the Statute of the Special Tribunal for the Crime of Aggression (STCoA), establishing an independent mechanism to prosecute those most responsible for the Russian invasion against Ukraine, filling the gap left by the ICC’s jurisdictional limits. The Statute adopts the Rome Statute’s definition of the crime of aggression (although without its specific sub-parts), but provides for immunity of the troika beyond issuance of an indictment.
Relatedly, the International Centre for the Prosecution of the Crime of Aggression (ICPA), hosted at the European Union Agency for Criminal Justice Cooperation (Eurojust), has coordinated investigative efforts of the crime of aggression among participating countries, while also collaborating with the ICC Office of the Prosecutor. Using the Core International Crimes Evidence Database (CICED) to collate and analyze evidence, the ICPA has been designed to facilitate the preparation of cases for transfer to the Special Tribunal, consolidating investigative work and developing strategies to support accountability for the crime of aggression.
The Memorandum as a Tool for Prosecution
OSJI’s Memorandum for Prosecution is intended to support domestic and international efforts to hold Russian and Belarusian senior officials accountable for the continuing crime of aggression against Ukraine. It compiles open-source evidence and contextual analysis. In particular, it could be used by domestic prosecutors in jurisdictions where the crime of aggression has been criminalized. While this Memorandum relies on publicly available sources, its findings could be complemented by intelligence and evidence gathered by the ICPA to support future prosecutions before the Special Tribunal, Ukrainian domestic courts, or other domestic courts under the principle of universal jurisdiction.
