The Russian invasion of Ukraine in February 2022 has sparked an unprecedented and multi-level response to document and investigate the crimes committed during the course of the conflict.

At the domestic level, the Office of the Prosecutor General of Ukraine (OPG) is investigating Russian crimes of aggression and war crimes, as well as crimes against national security, such as treason and collaborative activities. War crimes proceedings were initiated against Russian military personnel, some of them being tried in absentia, and several Russian soldiers that were present at their trials were already sentenced in Ukraine. There has been no sign of criminal investigations or prosecutions of potential war crimes committed by the Ukrainian military.

At the international level, the Office of the Prosecutor of the International Criminal Court (ICC-OTP) opened an investigation on 2 March 2022 on the basis of two ad-hoc declarations lodged by Ukraine in 2014 and 2015. This investigation led to two arrest warrants issued against Vladimir Putin and his Children’s Rights Commissioner Maria Lvova-Belova on 17 March 2023 for the war crimes of unlawful deportation and transfer of children from occupied areas of Ukraine to the Russian Federation. In 2024, the court issued additional arrest warrants for four senior Russian military leaders, including former Defense Minister Sergei Shoigu. On 4 March 2022, the UN Human Rights Council established an Independent International Commission of Inquiry on Ukraine, which was mandated to investigate alleged violations of international human rights and humanitarian law. At the regional level, the OSCE’s Moscow Mechanism sent missions of experts and has documented war crimes and crimes against humanity, while the EU and the Council of Europe have put in place support and cooperation mechanisms.

In addition, several countries have opened national investigations into the situation, invoking universal or other forms of extraterritorial jurisdiction. Announcements to this effect have been made by states such as Poland, Lithuania, Sweden, Germany, Norway, Switzerland, France, Spain and Canada. To combine accountability efforts, Poland, Lithuania and Ukraine set up a Joint Investigation Team (JIT) in March 2022, which operates under the auspices of Eurojust and was later joined by the ICC-OTP, Estonia, Latvia, Slovakia and Romania. Since the legal framework for prosecuting crimes committed abroad varies greatly from country to country, it is difficult to make general statements about the scope and focus of these investigations. While some countries, such as Germany and Sweden, allow person-specific investigations to be opened without a territorial link, other countries, such as France and Switzerland, require the presence or even the residence of the suspect for doing so. This is why investigations in France, for example, reportedly focus on crimes committed against French nationals, as this does not presuppose such a territorial link.

The investigations currently being conducted by the ICC-OTP, the Joint Investigation Team, the Ukrainian OPG and war crimes units in third states should focus on high-level perpetrators and the structural dimensions of crimes. While prosecuting individual cases certainly sends an important signal in the fight against impunity, the structural patterns of the crimes committed must be at the center of investigative endeavors. The ICC arrest warrants against Putin and his Children’s Rights Commissioner Maria Lvova-Belova are a significant step in that direction, aiming for accountability for the unlawful deportation of Ukrainian children to the Russian Federation. Additionally, a survivor-centered approach must be maintained throughout all stages of investigations that also includes legal and psychosocial support. At the same time, investigating authorities must ensure that civil society perspectives are represented in the prioritization of investigations, with special attention given to marginalized and vulnerable groups of survivors. Ukrainian civil society can draw upon rich experiences and insights with regard to the documentation of war crimes gathered since the beginning of the armed conflict in 2014. It is of utmost importance to listen to their experiences, as well as to support and amplify their voices and demands. Local civil society groups are playing an indispensable role in supporting witnesses and survivors, especially in light of the lack of trust in state authorities that can be observed in many places. Special attention must be given to previously under-investigated crimes, with a focus on sexual and gender-based violence. These investigations must be carried out by specially trained personnel so that re-traumatization and secondary victimization are prevented. Investigations must examine the alleged crimes of all parties to the conflict, some of which date back to the outbreak of the armed conflict in 2014. Within these efforts, the coordination among relevant stakeholders is crucial to avoid the duplication of efforts.

After years of political deadlock, the Ukrainian Parliament finally voted to ratify the Rome Statute of the International Criminal Court in August 2024, and the implementing law was subsequently passed and signed by President Zelensky in October 2024. This came in the wake of tireless efforts on the part of both Ukrainian and international civil society to persuade Ukraine to take this step. 

Despite having already accepted the ICC's jurisdiction through two ad hoc declarations in 2014 and 2015, Ukraine had until recently shied away from becoming a party to the Rome Statute. After a lengthy process of constitutional amendments that removed alleged legal obstacles to ratification, there was no longer any reason not to accede to the Rome Statute. Nevertheless, Ukrainian officials repeatedly opposed ratification on the grounds that it would expose Ukrainian forces to possible international prosecution. Not only was this argument flawed – as the ad hoc acceptance of ICC jurisdiction already allowed for the prosecution of statutory crimes by all parties to the conflict – but it also exhibits a problematic and one-sided approach to justice.

To move beyond such restrictive reasoning, ratification was therefore a necessary and long-overdue step. However, Ukraine's commitment to justice still seems half-hearted in some respects. Invoking Art. 124 of the Rome Statute, it has declared that it won't accept the court's jurisdiction over possible war crimes committed by its own nationals for a period of seven years. This restrictive declaration not only represents a missed opportunity; it is also unnecessary. Any concerns about the possible prosecution of its own nationals could be addressed through effective domestic investigations, as the ICC only steps in when states are unwilling or unable to investigate. To avoid accountability gaps resulting from limited acceptance of the ICC's jurisdiction over war crimes, Ukraine must ensure that any possible incidents involving its nationals are investigated impartially and effectively.

Since Russia's attack on Ukraine in 2014, the shortcomings of Ukrainian legislation regarding the prosecution of international crimes have been a matter of concern. The Ukrainian Criminal Code entered into force in 2001, at a time when accountability for international crimes was neither a priority nor of immediate practical relevance. Although the Rome Statute had already been adopted at that time, the legislature stopped short of incorporating crimes against humanity and the principle of command responsibility into domestic law. Provisions on war crimes and the crime of aggression were introduced, but they are not sufficiently aligned with international standards. After years of advocacy by civil society and a failed reform process, the Ukrainian Parliament finally adopted amendments to the Criminal Code in October 2024 as part of the Rome Statute implementation process. This law not only introduced crimes against humanity and command responsibility, but also the principle of universal jurisdiction, which will allow Ukraine to prosecute international crimes committed abroad by or against foreign nationals. However, due to the principle of non-retroactivity, these provisions are likely to apply only after their entry into force, thus excluding crimes committed before October 2024.

On a practical level, the ongoing war of aggression poses significant challenges to the Ukrainian legal system. The first trials of alleged Russian war criminals who have been physically detained have raised concerns about due process, with exceptionally short trials and confessions obtained under unclear circumstances. The fact that most of the trials are being held in the absence of the accused raises additional questions of proper notification and effective defense. While Ukraine's efforts to ensure accountability are to be welcomed and supported, real justice can only be achieved on the basis of laws and procedures that meet international standards. Ukraine must therefore ensure that these standards are met, in line with the demands of Ukrainian civil society.

The principle of universal jurisdiction must be strengthened. Countries with laws that only provide for a limited version of universal jurisdiction, such as France and the Netherlands, need to expand these laws to permit broader jurisdiction in international crimes cases. The ongoing conflict underlines the need for investigations unconstrained by presence requirements of suspects and similar limitations. In the case of the Netherlands, for instance, Dutch war crimes units are not permitted by law to investigate until a suspect is present in the Netherlands, meaning that supporting the ICC with national investigators and forensic experts is the only option available for engaging in investigations that do not meet these narrow requirements.

The crime of aggression is by definition a leadership crime. However, Putin, as long as he remains sitting president, enjoys immunity from prosecution for international crimes before national courts. Similarly, the ICC, which by virtue of its international character would be best placed to prosecute the crime, cannot take actions concerning the Russian war of aggression. It lacks jurisdiction over the crime of aggression when it is committed by nationals of states that are not party to the Rome Statute, such as Russia. A Security Council referral could theoretically bridge that gap, but Russia’s veto is certain. The crime of aggression in this regard is different from war crimes and crimes against humanity, which can be prosecuted when committed on the territory of a state that has either ratified the Rome Statute or accepted ICC jurisdiction through an ad-hoc declaration, as Ukraine has done. This exception goes back to the 2010 Kampala Conference, where the jurisdictional regime for the crime of aggression was specifically negotiated. Powerful states like the US pushed for limiting the court’s jurisdiction over the crime of aggression to shield their own nationals from prosecution. In light of these obstacles, some stakeholders are calling for the establishment of a special tribunal for the crime of aggression.

A special tribunal for the crime of aggression would perpetuate problematic double standards and selective justice, considering that representatives of the same states that once lobbied to limit the jurisdictional power of the ICC regarding this crime are now supporting the idea of such a tribunal. This sends a fatal message that undermines equal justice, implying that aggressive warfare by certain state actors is worthy of prosecution, while the representatives of other states continue to enjoy impunity. The only way to close this impunity gap in an equitable and sustainable manner is to amend the Rome Statute, giving the ICC jurisdiction over all acts of aggression committed against its member states or those who accept its jurisdiction.

Another model for avoiding selectivity would be a hybrid tribunal on all international crimes, as has been demanded by many members of Ukrainian civil society. Such a mechanism would be composed of both national and international professionals and embedded within the Ukrainian legal system. Not only would it be beneficial for furthering international criminal justice but also for strengthening the Ukrainian justice system, enhancing domestic capacities, while ensuring that due process is followed. It would thus provide an adequate answer to the doubts expressed by Ukrainian civil society regarding Ukraine’s domestic capacities to handle cases of mass atrocities.

Victims who have fled to the European Union are entitled to a number of rights under the EU Victims’ Rights Directive, even if the crimes were committed outside the EU. As part of the ongoing investigations in many European countries under the principle of universal jurisdiction, victims should be fully informed about their rights under the directive and how they can best exercise them. This includes low-level access to legal and psychosocial support. Legal support should include advice on war crimes investigations, witness protection, as well as on migration status and related questions. Such forms of support would mitigate the risk of duplicating survivor interviews by ensuring that survivors in stable conditions would provide better quality testimonies. However, there are no adequate support mechanisms in place across Europe either for victims of international crimes from Ukraine or other countries.