Symposium on Prosecuting Heads of State for International Crimes: The Special Tribunal for the Crime of Aggression against Ukraine and Immunities

[Noëlle Quénivet is Professor in International Law at the Bristol Law School of the University of West of England (UK). She holds a LLM in International Human Rights Law from the University of Nottingham and a PhD in Law from the University of Essex]

When the Council of Europe and Ukraine signed an agreement on 25 June 2025 establishing the Special Tribunal for the Crime of Aggression against Ukraine (STCoA), many hoped it would sweep aside both the functional and personal immunities of the Russian and Belarusian “Troikas” (the Head of State, the Head of Government and the Minister of Foreign Affairs) and deliver a Nuremberg-style reckoning for an unlawful war. 

However, if one was expecting a tribunal that simply declares “no immunity,” the Statute may feel underwhelming. Yet, I argue that the Statute complies with the law as spelled out in the Arrest Warrant Case. The International Court of Justice (ICJ) emphasized that there are several options for prosecuting the Troika. One relates to prosecution before “certain international criminal courts”, and another three relate to prosecution in national courts: 1) prosecution in the courts of their own State; 2) prosecution by a foreign court following the issuance of a waiver by the State of nationality; 3) prosecution by a foreign court of former officials. This post argues that the STCoA provides for the second and third domestic options.

By basing its jurisdiction on Ukraine’s territorial competence and by recognizing immunities ratione personae for sitting leaders while excluding immunity ratione materiae for aggression, the drafters chose doctrinal conformity over lege ferenda shortcuts. That choice might be criticized, but it is sound: it keeps the door to leadership accountability open without stepping outside the law. 

This post provides an overview of the law of immunities regarding the Troika. It examines what the Statute provides regarding immunities and explains why, in this regard, it resembles a foreign national court.  

Immunities of the Troika and the Crime of Aggression

Aggression’s modern genealogy, from Nuremberg’s “crime against peace” to Kampala’s Article 8 bis, marks it as a leadership crime (para 21 of Commentary on Article 7 of ILC Draft Articles on Immunity): liability is limited to those “in a position effectively to exercise control over or to direct the political or military action of a State” (Article 8bis Rome Statute). The STCoA adopts that leadership focus and personal jurisdiction, targeting those “in a position effectively to exercise control over or to direct the political or military action of a State” (Article 2 STCoA Statute) and those “who bear the greatest responsibility for the crime of aggression against Ukraine” (Article 1 STCoA Statute). Think here: heads of state and government and foreign ministers on both the Russian and Belarusian sides. That is, however, precisely where immunities bite the hardest. 

International law accords the “Troika” full personal immunity (immunity ratione personae) from foreign criminal jurisdiction while in office (Article 3 of ILC Draft Articles). It applies to official or private acts committed before or during their tenure in office. It should be seen as procedural (i.e. preventing a case from proceeding), temporary and not likened to impunity, as it is a bar (para 8 of Commentary to Article 1 of ILC Draft Articles) that lifts when the official leaves office or when the State grants a waiver. This is clearly explained in the landmark ICJ’s Arrest Warrant case and the International Law Commission’s (ILC) draft articles on immunity of State officials. 

Members of the Troika are also, as State officials, granted functional immunity (immunity ratione materiae) (Article 5 of ILC Draft Articles). This type of immunity continues after they leave office, as they benefit from immunity for all acts committed whilst in office, though not for acts committed prior or subsequent to that post. Additionally, they benefit from immunity for personal acts performed during that time (Article 6 of ILC Draft Articles). Yet, there are “exceptions to the immunity ratione materiae of State officials with respect to several crimes under international law” such as genocide, crimes against humanity, war crimes, etc (General Commentary under para 69 of ILC Draft Articles and Article 7 ILC Draft Articles). 

That being said, two issues must be noted. First, some ILC members (Commentary on Article 7 ILC Draft Articles) opposed Draft Article 7 on the ground that it did not reflect the current state of international law. In 2023, states queried the non-application of immunity to crimes under international law (see de Andrade Pacheco). In 2025 the Special Rapporteur asserted that the latest developments in international law “further support the need for including a draft article on the exceptions to this type of immunity” (para 53). The better view appears to be that this draft article “represents the progressive development of international law, not existing international law” (McDougall, p. 80). Second, the crime of aggression, often considered the crime of all crimes, was, until very recently, not included in that list of exceptions. In the 2022 Commentary on Draft Article 7, the then Special Rapporteur noted that the members disagreed on its inclusion. Heller (p. 12) observed that it was not possible at the time to provide a “definitive conclusion concerning the availability of functional immunity for the crime of aggression”. The ILC’s latest work now includes in Article 7(1)(g) the crime of aggression. According to these latest amendments, it is unlikely that the members of the Troika can rely on immunity ratione materiae to evade accountability for the crime of aggression. 

Ways to Avoid the Immunity Bar and What the Statute Provides

That the immunities of the Troika are discussed under the heading of national/foreign court might be surprising to some. Yet, the Special Tribunal’s jurisdiction is based on Ukraine’s sovereign right to prosecute the crime of aggression committed on its territory, as explained in Article 1 STCoA Statute: “Such jurisdiction is based on the territorial jurisdiction of Ukraine.” Ukraine is asserting its territorial jurisdiction over crimes committed on its territory and those initiated abroad but completed within its borders, exercising its right to enforce its own criminal jurisdiction (General Commentary under para 69 of LC Draft Articles).

The STCoA recognizes immunity ratione personae for the Troika. According to Article 23(5) STCoA Statute, if a member of the Troika is indicted, the Pre-Trial Judge must not confirm the indictment until that person is no longer in office or a waiver has been granted. Article 25(2) STCoA Statute reinforces that, for such individuals, the Pre-Trial Judge must suspend proceedings as set out in Article 23(5). This structure is fully compliant with international law on immunities before foreign courts. First, it is in line with Article 4(2) ILC Draft Articles, which states that members of the Troika cannot be prosecuted whilst in office. The Statute recognizes the Troika’s immunities ratione personae. Second, it acknowledges that a waiver can allow the tribunal to proceed with the charges. This point was made by the ICJ in the Arrest Warrant case regarding prosecutions by foreign courts. Under Article 12 ILC Draft Articles, the waiver must be issued by the State of the official, be expressed and in writing, communicated through official means and be irrevocable. Third, this mechanism recognizes that the enforcement of the law is only procedural (i.e. the suspension of the enforcement) and temporal since, once the person “no longer holds that office or an appropriate waiver has been presented” (Article 23(5) STCoA Statute), the proceedings can resume. 

Noteworthy in this context is that Article 25(2) of the Statute uses the word “suspend”. This mirrors the ILC commentary’s insistence that personal immunity is a temporary, procedural bar. This, in effect, confirms that the Tribunal grants immunity ratione personae to such individuals in much the same way (using the second and third options spelled out in the ICJ Arrest Warrant case) as a foreign court would.  

Further, under Article 24(4) STCoA Statute, the Prosecutor must refrain from “measures of constraint” vis-à-vis sitting Troika members. The ILC Draft explains that the obligation to consider immunity arises only when a foreign official might be affected by criminal actions taken by another state. This includes activities like investigations and prosecutions, but only if the official is hindered from performing their duties. The commentary on Draft Article 9 makes clear that initiating a preliminary investigation or criminal proceedings does not constitute a violation of immunity, provided it does not impose any legal obligations on the official. Gathering evidence that does not restrict foreign officials, including the Troika, is permitted. Likewise, simply inviting a foreign official to testify is acceptable (Case Concerning Certain Questions of Mutual Assistance in Criminal Matters, para 171). In contrast, requiring their appearance in court or requesting their extradition would not. The term “measures of constraint” mentioned in Article 24(4) STCoA Statute is not fully defined, but it should align with international law. Nuridzhanian contends that it is unclear if issuing an indictment counts as a measure of constraint. However, whilst Articles 23(5) and 25(2) do not permit confirmation of the indictment or the issuance of an arrest warrant against a member of the Troika, an indictment is still possible.

With regard to immunities ratione materiae, Article 23(4) STCoA Statute declares that they “shall not apply before the Special Tribunal” for the crime of aggression, thereby ensuring that once personal immunity falls away, official capacity will not shield State officials, including the Troika. It is argued that this position aligns with the ILC’s evolving Draft Article 7 approach to ratione materiae exceptions to immunity for international crimes. Whilst that position is contentious in some quarters, it is also where the law is heading. And the STCoA is only following that trend. 

Chances of Prosecution

One wonders why the drafters bothered to design such a legal construct, given that it cannot issue arrest warrants and the chances of capturing the Troika whilst in power are close to null. 

Critics argue that the STCoA’s inability to issue arrest warrants against incumbents diminishes its expressive and deterrent value (McDougall p. 80). In contrast, Trahan (p. 688), notes that indictments, even if unenforceable for the moment, carry powerful expressive force. Indeed, historical experience suggests that indictments can have tangible effects even before custody is secured. Axworthy’s account of Milošević’s indictment illustrates how legal action can erode domestic authority, alter political behaviour, and accelerate diplomatic engagement: “make no mistake: It can work.” As Olley observes (p. 78), for many, the symbolic global significance of an aggression indictment against a sitting leader outweighs the practical hurdles of securing custody.

Whilst personal immunity for Troika members would become a “non-issue” once they no longer hold office (see Heller), the debate is not moot as Article 28 STCoA Statute allows prosecution in absentia, which means that it is possible to indict a sitting member of the Troika. The Parliamentary Assembly of the Council of Europe had in 2024 suggested that:

“its statute could foresee the possibility of in absentia proceedings before the trial stage, for instance hearings for the confirmation of charges in the absence of the suspect”

(para 13.9.7)

Conducting trials in absentia is a controversial topic in international law. On the one hand, the presence of the defendant is crucial to safeguard their rights and ensure that proceedings are conducted fairly. Trials in absentia can lead to denial of justice and arbitrary convictions. Nevertheless, allowing in absentia trials can also serve as a deterrent and fight impunity. Two “special” tribunals provided for in absentia trials: the Nuremberg tribunal and the Special Tribunal for Lebanon. Although the latter complied with human rights law, it faced criticism  (Lobel and Milaninia and Council of Europe p. 3). Whether the STCoA wants to pursue that route is primarily a prosecutorial decision that depends on the likelihood of arresting Troika members in the near future. It should be noted that, in contradistinction to the Special Tribunal for Lebanon, which had limited the retrial to the same tribunal (Article 22(3)) and thus had put a temporal limit on that right, Article 28(3) STCoA refers to a retrial “before the Special Tribunal or a successor mechanism”. Accordingly, it preserves the right to a retrial through either the Special Tribunal or another forum, and therefore, if it proceeds with trying Troika members in absentia, it would be possible to hold a retrial in the presence of the accused. 

This does not erase the practical reality that the immediate apprehension of Russian or Belarusian leaders is unlikely. For example, although an arrest warrant has been issued by the International Criminal Court (ICC) against Putin for war crimes under Articles 8(2)(a)(vii) and (b)(viii) for the unlawful deportation and forcible transfer of children from occupied areas of Ukraine to Russia, Tajikistan, a State Party to the ICC Statute did not arrest him when he visited the country in October 2025. 

Conclusion

The STCoA’s immunity regime will disappoint those seeking an immediate solution to the leadership immunity issue. However, it should reassure those who value the integrity of international criminal law. By considering personal immunity as a suspensive obstacle and eliminating functional immunity for aggression, the Statute ensures that holding leaders accountable remains legally feasible. Effective accountability is ensured when institutions have legal credibility. The STCoA, by basing its jurisdiction on Ukraine’s territorial jurisdiction and providing ratione personae immunities to the Troika, closely resembles the limitations faced by foreign courts. It chooses a path that remains within the bounds of law while still emphasizing individual responsibility for a clear violation of the UN Charter’s use-of-force regime.