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How to Achieve Accountability for the Crime of Aggression

How to Achieve Accountability for the Crime of Aggression

How to Achieve Accountability for the Crime of Aggression

Since the Russian invasion of Ukraine that began on Feb. 24, the machinery of the international legal system has sprung into action at unprecedented speed. On Feb. 28, International Criminal Court (ICC) Prosecutor Karim Khan began investigating war crimes and crimes against humanity in Ukraine in the current conflict. Neither Ukraine nor Russia is party to the Rome Statute, which created the ICC and gives it jurisdiction, but Ukraine submitted to the jurisdiction of the court in 2013 and extended that submission indefinitely in 2014. In recent weeks, forty-one countries have referred the situation in Ukraine to the Prosecutor, prompting the ICC’s rapid response. Yet the ICC does not have jurisdiction over what may be the most grave legal violation involved in the invasion: the act of aggression itself. Because of a distinctive feature in its statute, the ICC cannot exercise jurisdiction over the crime of aggression by non-state parties—including Russia.

As a result, there have been efforts to find an alternative international forum in which to try the crime of aggression. Perhaps the leading proposal is to establish an international or hybrid tribunal under the joint auspices of Ukraine and the United Nations General Assembly. Several international lawyers have supported this approach. They note that such an international tribunal would be able to pierce the veil of head of state immunity. They point to the Special Court for Sierra Leone, created by agreement between Sierra Leone and the United Nations, and the Extraordinary Chambers in the Courts of Cambodia, formed by agreement between Cambodia and the United Nations, as precedents. There are also other proposals for establishing a tribunal, which we discuss below.

Establishing a court through an agreement between Ukraine and the United Nations or through another mechanism raises questions of whether such an arrangement is consistent with Ukrainian law. While the Ukrainian Constitution would permit the Ukrainian government to enter an agreement to create a new court, there are two important conditions. First, the court must be “international,” not hybrid or an extraordinary chambers of a domestic court. Second, it must not be designed or described as “complementary” to the judicial system of Ukraine (a term used, for example, by The Elders, a group of senior foreign policy leaders, in endorsing the proposal). These conditions leave ample room for establishing a tribunal with a solid legal foundation.

A New Court Must be “International”

Article 125 of the Ukrainian Constitution states that, “The establishment of extraordinary and special courts shall not be permitted.” To some international lawyers, this may appear to be a direct reference to the Special Court for Sierra Leone or the Extraordinary Chambers in the Court of Cambodia. But that is wrong.

This clause is directly rooted in Ukraine’s status as a post-Soviet state. At the time the Constitution was adopted in 1996, the memory of special and extraordinary tribunals which took place during the Soviet era was still fresh. “Extraordinary and special courts” essentially were forms of extrajudicial simplified “justice” serving totalitarian goals, such as NKVD Troika, or Special Troika, during The Great Purge and special courts in the Gulag system, as well as various military tribunals created in the former Soviet Union. “Special courts” are understood as separate domestic judicial institutions with their own system for consideration of certain categories of cases (usually criminal). “Extraordinary courts” are considered to be domestic courts that are formed to consider a specific (usually criminal) case on the basis of a special act of the relevant public authority.

Article 125 of the Constitution must also be read alongside the Law on the Judiciary and the Status of Judges. Article 3 of that law has a similar provision, but the title of the article is “Judiciary system in Ukraine.” Hence, the consensus among legal jurists in Ukraine is that Article 125 sets up a prohibition on creating special and extraordinary courts within the system of courts in Ukraine and does not place a limit on international judicial institutions.

Indeed, after Ukraine signed the Rome Statute in 2000, the President of Ukraine filed a constitutional petition with the Constitutional Court of Ukraine (CCU) seeking an opinion on the constitutionality of ratifying the Rome Statute. The Constitutional Court concluded (para 2, section 2.1 of the CCU conclusion No 3-в/2001 dated July 11, 2001, case No 1-35/2001) that this clause does not apply as such to the ICC:

By its nature, the International Criminal Court is an international judicial body established with the consent of the member states of its constituent instrument, the Statute, which is based on respect for human rights and freedoms, including the establishment of appropriate jurisdictional mechanisms to ensure fair justice. Therefore, the International Criminal Court cannot be referred to extraordinary and special courts, the establishment of which is not allowed in accordance with part five of Article 125 of the Constitution of Ukraine. Extraordinary and special courts within the meaning of this article are, firstly, not international but national courts, and secondly, courts, which do not properly follow the procedures established by law and are established to replace ordinary courts.

In short, if a court to try the crime of aggression is created not as a domestic court but as a wholly international one, then Article 125 of the Ukrainian Constitution is not a bar to establishing such a tribunal to address the crime of aggression.

The Court Must Not be “Complementary” to the Judicial System of Ukraine

In the same decision, however, the CCU provided a narrow interpretation of Section VIII of the Constitution that created a different impediment to ratifying the Rome Statute–one that has some implications for the current situation. The CCU noted that, under the Rome Statute, the ICC can take action on the initiative of a State party or when the State under whose jurisdiction a person suspected of committing an offense under the Statute is “unwilling or unable to investigate or prosecute properly.” Specifically, the CCU pointed to paragraph 10 of the Preamble and Article 1 of the Rome Statute, according to which “the International Criminal Court … complements national criminal justice authorities” (emphasis added). The CCU appears to have interpreted these provisions in the Rome Statute referencing the ICC’s “complementary” jurisdiction to mean that jurisdiction of the ICC is additive. As a consequence, the CCU found the Rome Statute inconsistent with Article 124 of the Ukrainian Constitution, which restricts the juridical power in Ukraine to the courts and prohibits delegation of those functions to other bodies.*

Importantly, the CCU made clear that this impediment does not extend to other international courts to which Ukraine is or may be a party. The European Convention of Human Rights (ECHR), to which Ukraine has been a party since 1997, expressly provides that the European Court of Human Rights (ECtHR) may deal with a matter only “after all domestic remedies have been exhausted.” Unlike the Rome Statute, the CCU explained, the ECHR is consistent with the Constitution. Such an arrangement, the CCU noted, is specifically permitted by part four of Article 55 of the Constitution, which provides: “After exhausting all domestic legal instruments, everyone shall have the right to appeal for the protection of his/her rights and freedoms to the relevant international judicial institutions or to the relevant bodies of international organisations of which Ukraine is a member or participant.” In a somewhat cryptic passage, the court explained that “unlike international judicial bodies, provided by part four of Article 55 of the Constitution of Ukraine, which by their nature are auxiliary means of protection of rights and freedoms of man and citizen, the International Criminal Court complements the system of national jurisdiction” (emphasis added). It continued, “The possibility of such an addition to the judicial system of Ukraine is not provided for by Section VIII ‘Justice’ of the Constitution of Ukraine [Article 124].” (Meanwhile, the CCU considered and dismissed other constitutional concerns that had been raised.)

Complicating interpretation of these passages, the CCU did not address the structure of the jurisdiction of the ICC–or that complementarity is in fact intended not to deprive domestic courts of control but just the opposite. Instead, it focused simply on the Rome Statute’s self-description of its jurisdiction as “complementary.” In drawing the distinction between the ICC and the ECtHR, it did not clarify which of the many differences between the courts was critical to its analysis. It noted two differences: (1) the proceeding in the ECtHR allows persons who have exhausted their domestic remedies to pursue their rights and freedoms in an international body, and (2) a person may apply to ECtHR and institutions like it only after the exhaustion of domestic remedies. No criminal proceeding could satisfy the first. And yet the CCU never ruled out the possibility that a criminal court could pass constitutional muster–rather it focused on the ICC’s self-described “complementary” jurisdiction. This suggests that the second difference was the critical one.

In 2016, the Ukrainian parliament amended the Constitution to allow for ratification of the Rome Statute by adding a provision to Article 124 stating that “Ukraine may recognise the jurisdiction of the International Criminal Court subject to the conditions determined by the Rome Statute of the International Criminal Court.” At the same time, it deleted paragraph 3 of Article 124, one of the two provisions that the CCU had cited as an impediment to ratification of the Rome Statute.

Furthermore, paragraph 1 of the Article 124, which is the only one of the two problematic provisions that remains, was never meant to limit the jurisdiction of international courts. In 1996, when the Constitution was first adopted, Ukraine had little experience with the rule of law, and paragraph 1 was an attempt to consolidate juridical power on the national level in courts, not to limit international tribunals. It is generally understood that it was created to outlaw the previously existing practice of serving justice through courts delegating their powers to agencies or commissions. Indeed, it is most likely that the possibility of international tribunals was not envisioned by the Constitutional drafters.

Based on the 2001 decision of the CCU, the 2016 amendments to the Constitution removing one of the two problematic provisions, and the history of Article 124, it appears likely that as long as a new international court to try the crime of aggression is not described as “complementary” but instead as “auxiliary,” then there is no constitutional impediment or need for a constitutional amendment in order to establish an international court. All that said, it is important to acknowledge that it is possible the CCU would see the legal matter differently were it to address the issue since the law is far from definitively settled.

Alternative Paths to Accountability

In addition to establishing a tribunal under the joint auspices of Ukraine and the UN General Assembly, there are a number of alternative approaches to providing accountability for the crime of aggression. These paths are not necessarily mutually exclusive or inconsistent. Indeed, domestic prosecutions in Ukrainian court can and likely will proceed alongside any effort to establish an international court.

Domestic Prosecutions in Ukrainian Courts

All of the discussion above suggests that while there is an argument for creating a new international tribunal to try the crimes of aggression being committed in Ukraine, it may be equally important–if not more important–to move quickly to provide resources to the Ukrainian judicial system to proceed with domestic prosecutions. As part of that process, support also should be provided for proper evidence collection to enable future prosecutions of not only the crime of aggression, but also war crimes and crimes against humanity.

Ukrainian law specifically criminalizes the crime of aggression. Article 437 of the Criminal Code of Ukraine addresses “Planning, preparation and waging of an aggressive war.” (The law can be found here in English.) The Article provides:

Article 437. Planning, preparation and waging of an aggressive war

1. Planning, preparation or waging of an aggressive war or armed conflict, or conspiring for any such purposes

shall be punishable by imprisonment for a term of seven to twelve years.

2. Conducting an aggressive war or aggressive military operations

shall be punishable by imprisonment for a term of ten to fifteen years.

The crime of aggression is therefore a special grave crime against Ukraine, and therefore is punishable according to the Criminal Code of Ukraine even if it is committed outside of the country by a foreigner.

Article 6 of the Code makes clear that those who commit this offense in the territory of Ukraine shall be criminally liable, and Article 8 expressly extends the Code’s provisions to foreign nationals, including Russians.

The Ukrainian Prosecutor General Iryna Venediktova already has thousands of active investigations of war crimes in Ukraine. She could potentially proceed with prosecutions of the crime of aggression as well. However, evidence of the crime of aggression–which is by its nature a leadership crime–can be more difficult to gather. Therefore support for this work–including funding, assistance with proper evidence collection and handling, and legal expertise–would be essential to make it possible for the cases to proceed and succeed.

It is important to note, however, that there could be drawbacks to relying entirely on Ukrainian courts. In 2019, a Ukrainian court found the former president Viktor Yanukovych guilty of treason and complicity in the crime of aggression. The trial took place in absentia; Yanukovych was invited to testify via video link, but failed to appear. Sentencing Yanukovych to 13 years in prison, Ukrainian courts demonstrated their capacity to adjudicate such cases. Yet Yanukovych has not been incarcerated and continues to live in Russia. His sentence would begin “the moment he is detained,”if he is ever detained. Given the difficulty of gaining custody of many of the likely defendants in the current situation, Ukrainian courts would face the same challenge to impose their own judgments, leading to a general loss of accountability in spite of any successful prosecutions. Furthermore, the prosecution against Yanukovych has been criticized for proceeding in the absence of the defendant, and such trials in absentia generally are considered to raise human rights concerns. If potential defendants are tried under similar circumstances, this could reduce the willingness of the international community to assist in bringing those who are convicted into custody or to otherwise support such prosecutions. An arrest warrant from an international court, by contrast, is likely to elicit widespread cooperation. This means that, at a minimum, those indicted are unlikely to be able to travel outside of Russia even if they are not brought to justice in a courtroom.

(A number of other states, including Lithuania and Poland, have also begun domestic investigations of the crime of aggression. But there are concerns that states may not be entitled to exercise universal jurisdiction over aggression.)

What’s more, national courts may run into significant legal difficulties due to head of state and other immunities for senior Russian officials in a way that an international court would not.

An International Tribunal Established by UN General Assembly

It is also worth considering the possibility of creating an international tribunal through the UN General Assembly to try the crime of aggression without a formal agreement between the UN and Ukraine. After all, Russian aggression is not simply an offense against Ukraine, but an affront to the entire international legal order. While the crime of aggression has occurred on Ukrainian soil, and Ukrainians are the ones who have suffered horribly, Russia’s flagrant violation of the prohibition on the use of force contained in Article 2(4) of the UN Charter fundamentally threatens international peace and security.

An international tribunal with jurisdiction over the crime of aggression alone poses little risk of infringing on Ukrainian sovereignty, and would presumably find no objection by the Ukrainian government. There is no reason to believe that any Ukrainian will be prosecuted by a new court, hence the sovereignty issues for Ukraine are not as salient as they would be were Ukrainians to come before it. An international tribunal, moreover, could collaborate closely with the Ukrainian government and prosecutor general even in the absence of a formal agreement jointly creating the court.

However, some have raised the concern that creating an independent ad hoc court could exceed the powers of the General Assembly. When the General Assembly has been involved in the creation of prior ad hoc tribunals (including the Extraordinary Chambers in the Courts of Cambodia), it has been with the involvement of the target state.

A Special Tribunal Modeled on Nuremberg

An approach endorsed by former British prime minister Gordon Brown and several other heads of state and legal experts is to create a special tribunal modeled on Nuremberg that would be established by a group of supportive states. This approach would likely avoid the constitutional issues raised above, because it would not require an agreement with the Ukrainian government. This approach has drawn criticism, however, on the ground that a tribunal created by a few states would not have the legitimacy of one created under the auspices of an international organization. Nuremberg, on which this tribunal would be patterned, drew accusations of victor’s justice, as did its companion tribunal in Tokyo. A new tribunal established on the same model might face similar challenges, as well as charges of selective justice.

A Hybrid Tribunal Under the Auspices of the Council of Europe

Another approach recently proposed by Kevin Jon Heller would be to establish a hybrid tribunal under the auspices of the Council of Europe (CoE)–an “Extraordinary Ukrainian Chamber for Aggression” (EUCA). Ukraine is already a member of the CoE. Heller proposes that Ukraine ask member governments to adopt a common policy to establish a hybrid tribunal–a proposal that would require unanimity among the members. A treaty creating the EUCA and establishing its structure would provide, inter alia, that the EUCA would be part of Ukraine’s judicial system. Such a proposal might take advantage of the CCU’s approval of the existing CoE institution–the ECtHR.

However, making the EUCA a part of Ukraine’s judicial system, as currently proposed, raises a set of constitutional concerns regarding how it would fit with a number of clauses of Art. 125 of the Ukrainian Constitution. First, if the EUCA becomes a part of the national judiciary, it is likely to be seen as an “extraordinary court” because it will satisfy both criteria laid down by the CCU: (1) it will have a procedure for deciding cases which is distinct from the rest of procedure rules existing in Ukraine and (2) it will be created to replace other domestic courts which currently have jurisdiction over the matter. Second, under Art. 125, any court “shall be formed, reorganised, and liquidated by law, the draft of which is submitted to the Verkhovna Rada of Ukraine [the Ukrainian Parliament] by the President of Ukraine after consultations with the High Council of Justice.” This process does not provide for, and might not permit, international involvement in the creation of a domestic court. Third, the creation of the EUCA might be seen as a challenge to the supremacy of the Supreme Court in the domestic system of the judiciary. Finally, the EUCA might be determined not to fit within the scope of the principles of territoriality and specialization on which the Ukrainian judiciary is based. As a consequence, if any new tribunal is established under CoE auspices, it must be designed as a purely international court rather than as a hybrid one.

Amend the Ukrainian Constitution

One might ask, if the Ukrainian Constitution is such an impediment, why not amend it? Unfortunately, such an amendment is likely impossible under current conditions. Part 2 of Art. 157 of the Constitution bans any constitutional amendments under conditions of martial law or a state of emergency. Revoking martial law, which was imposed on Feb. 24, 2022, would substantially reduce the government’s capacity to operate under the conditions of the military invasion, including but not limited to undermining the ability to conscript soldiers, mobilize the economy and lawfully restrict some constitutional human and civil rights and freedoms.

And even if martial law were revoked, a draft law introducing an amendment to the Constitution would require the approval of two consecutive regular sessions of the Parliament (with the majority and two-thirds of the constitutional composition of the Verkhovna Rada voting in favor), and would require the conclusion of the CCU on the constitutionality of the amendment. In the most optimistic and hardly likely scenario, the process would take at least a year.

(Yet another approach would be to amend the Rome Statute to allow the ICC to exercise jurisdiction over non-state parties for the crime of aggression. But that process would likely take years, not months, and face significant political obstacles.)


Not since the years immediately following World War II has the international community been so united in condemnation of an illegal aggressive war. One hundred and forty states voted in favor of the General Assembly Resolution deploring the aggression by Russia “in violation of Article 2(4) of the Charter” with only five states, including Russia, voting against it. States supporting the Resolution demanded that Russia immediately cease its use of force against Ukraine and refrain from any further unlawful threat or use of force against any Member State. And yet Russia continues to wage aggressive war in Ukraine. If ever there were a time to prosecute the crime of aggression, this is it. Finding a way to do so, consistent with both international and Ukrainian law, is a key step toward providing accountability for Russia’s decision to place not only the people of Ukraine, but also the entire international order, at grave risk.

Image: A woman with a Ukrainian flag stands outside the International Criminal Court on the first day of hearings on March 7, 2022 in The Hague (Photo by Michel Porro/Getty Images).