2022.11.10

The Punishment of War Crimes in Ukraine

Kuniko Ozaki
Specially-Appointed Professor, Faculty of Law, Chuo University
Areas of Specialization: International Criminal Law and International Human Rights Law

1. What are the "core crimes"?

The Russian invasion of Ukraine in February 2022 has raised many questions that have shaken the post-World War II international legal order. Needless to say, the most pressing issue is an act of aggression by a permanent member of the Security Council, which violates the core principles enshrined in the UN Charter, including the principle of non-use of force. Another aspect of the invasion which has shocked international society is the various atrocities committed against civilians, mostly by Russian forces, during the invasion. According to media reports and published investigation results, many of these atrocities are considered to fall under the category of war crimes. Furthermore, there is a possibility that Russian forces have committed crimes against humanity (and genocide).

Genocide, crimes against humanity, war crimes, and crimes of aggression are classified as the "core crimes" in international law. These are the most serious crimes which violate the shared values of international society. (This article does not address crimes of aggression.)

The term "genocide" refers to specific acts such as killing members of a group committed with intent to destroy, in whole or in part, a national, ethnical, racial or religious group. The term "crimes against humanity" refers to murder, extermination, enslavement, deportation, sex crimes, etc., committed as part of a widespread or systematic attack on civilians.

Although war crimes cover a wide range of conducts, they mainly focus on acts which seriously violate the 1948 Geneva Conventions and the 1977 Additional Protocol (First). This includes the killing, torture or inhumane treatment of civilians and prisoners of war, and unlawful deportation and expulsion, deliberate attacks on civilians, looting, and sexual violence.

The core crimes are crimes under international law (regardless of whether or not they constitute crimes under the domestic law of each country) and perpetrators are subject to criminal responsibility under international law. International law concerning the core crimes developed rapidly after World War II through the formation of multilateral treaties and international customary law, and various international criminal courts were established after the Cold War. These rules of international law are also reflected in the domestic criminal laws of each country.

2. Role of the International Criminal Court

The first point of note in the investigation and prosecution of the core crimes committed in Ukraine is the role of the International Criminal Court (ICC). The ICC was established under the 1998 Rome Statute to punish individuals who commit the core crimes. The ICC consists of the Judicial Division with a two-instance system (presided over by a total of 18 judges, including preliminary trials) and an independent Office of the Prosecutor. As of August 2022, there are 123 State Parties to the Rome Statute. Jurisdiction extends to offenses committed within the territory of a State Party or committed by nationals of the State Party. The UN Security Council may also refer crimes committed in the territories of non-state parties to the ICC.

Neither Ukraine nor Russia is a party to the Rome Statute. However, Ukraine has accepted ICC jurisdiction for crimes committed on its territory after November 22, 2013. Therefore, in March 2022, ICC prosecutors launched an investigation into the situation in Ukraine.

The ICC does not prosecute all core crimes committed in given situation. The Rome Statute provides that the ICC will not accept a case if it is being investigated and prosecuted by a territorial state or if it is not of sufficient gravity to justify action by the ICC. The former is called the principle of complementarity, which states that prosecution should first be brought before the domestic courts of the concerned countries, and that the ICC will prosecute the case only if the concerned countries are unwilling or unable to do so. According to this principle, priority for the investigation and prosecution of the core crimes committed in Ukraine will be given to Ukraine, Russia and other concerned countries.

In other words, targets of prosecution by the ICC in the Ukrainian situation are those suspects whom Ukraine or other countries concerned is unable to prosecute for whatever reason, and those suspects who are commanders and leaders possessing grave responsibility for the series of crimes (in the case of crimes against humanity, this includes persons who formulated or promoted the policies underlying the crimes). However, prosecuting such suspects is not easy. For prosecution, in addition to collecting evidence that a crime was committed, it is also necessary to collect evidence linking the suspect (who may not be present at the scene) to the crime, and evidence regarding organizational functions and chain of command. If a high-ranking official in charge on the Russian side were to be investigated, the majority of evidence would likely exist in Russia, which is not a State Party to the Rome Statute and therefore would have no obligation to cooperate with the investigation. Furthermore, even if an arrest warrant were to be issued, Russia would have no obligation to extradite suspects. Even if the suspect had left Russia, there would be immunity under general international law if that suspect were a head of state of non-State Party.

3. Role of domestic courts

Many core crimes are also crimes under domestic law. War crimes committed by members of the Russian military have been investigated by Ukrainian authorities. In May, the first conviction by a Ukrainian court against a Russian soldier was handed down, and several other war crimes are currently undergoing trial. According to media reports, Ukrainian authorities are investigating more than 20,000 war crimes.

With regard to the core crimes, the establishment of universal jurisdiction under treaties or international customary law is considered permissible. Also due to the principle of complementarity adopted by the ICC, many countries, mainly in Europe, have enacted legislation to enable prosecution in their court of the core crimes committed by foreign nationals in foreign countries. Given the geographical proximity and active human traffic between Ukraine and these countries, it is possible that the victims may be nationals of these countries or that suspects may have traveled to these countries. Depending on the case, these countries may not extradite suspects to Ukraine and will prosecute them in their own courts.

4. Challenges ahead

Contemporary international law has developed a number of substantive and procedural rules and institutions for the punishment of the core crimes. However, the question of whether they are properly and effectively applied and operated is entirely another matter. Prosecution and punishment in domestic courts should be the basis. However, due to the nature of the core crimes, there is likely to be strong pressure due to political conditions and public sentiment. This may make it difficult to hold fair trials, including guaranteeing the rights of suspects and the accused. Moreover, the judicial systems of the countries where these crimes were committed are often weak, and problems such as corruption have been pointed out. Issues and limitations of the ICC are as discussed above.

Punishment of the core crimes in Ukraine will be a test of the international community's response to those challenges. For example, the Ukrainian judicial system is supported and monitored closely by mainly Western European countries. It is also necessary to pay close attention to the division of roles between the ICC, Ukraine and third-country courts based on the principle of complementarity, and the ability of the ICC to prosecute those who are truly responsible. How the international community will achieve fair and effective punishment of the core crimes is challenged.

Kuniko Ozaki

Specially-Appointed Professor, Faculty of Law, Chuo University
Areas of Specialization: International Criminal Law and International Human Rights Law


Kuniko Ozaki was born in Hiroshima Prefecture in 1956. She holds a Bachelor of Arts from the University of Tokyo and a Master of Philosophy in International Relations (Oxford University).
She joined the Ministry of Foreign Affairs in 1979. Before assuming her current position in 2021, she served as Professor in the Tohoku University Graduate School of Law, Director for Treaty Affairs for the United Nations Office on Drugs and Crime, and a judge at the International Criminal Court.

Her areas of expertise are international human rights law and international criminal law.

Her main written work includes An Introduction to International Human Rights Law and International Criminal Law (2nd Edition) (Shinzansha Publisher, 2021).