by Konstantinos D. Magliveras, Professor of Public International Law, University of the Aegean, Greece

I. Introduction

Since the Russian Federation’s so-called ‘special military operation’ against Ukraine in February 2022, there have been two major international processes for investigating and bringing to trial those allegedly responsible for criminal offences. Both processes started only a few days apart. First, the International Criminal Court (ICC). On 1 March 2022, the Office of the Prosecutor received a referral of the situation in Ukraine from Lithuania, followed by a joint referral by 38 states parties to the Rome Statute (1998), to which Ukraine acceded in January 2025. Presently, there are outstanding arrest warrants against President Putin and five other Russian nationals. Second, the UN Human Rights Council. On 4 March 2022, it established the Independent International Commission of Inquiry on Ukraine (Resolution 49/1), which is mandated to investigate alleged human rights and international humanitarian law violations connected to the aggression against Ukraine. The most recent Report of the Commission, whose mandate was last extended in April 2025 (Resolution 58/24), appeared in March 2025 (A/HRC/58/67).

In late June 2025, a third international process was added when the Council of Europe (CoE) and Ukraine signed the Agreement on establishing a Special Tribunal for the Crime of Aggression against Ukraine. It is important to note that this is a bilateral agreement: it was signed by the CoE Secretary General and the President of Ukraine, while the other Member States are not parties to it. The purpose of this note is to offer a brief overview of the Tribunal’s establishment and discuss some legal questions arising from the Agreement.        

II. The Special Tribunal’s legal set up and the question of complementarity

The Tribunal will operate on the basis of three instruments: the founding Agreement, the Statute and the Enlarged Partial Agreement on the Management Committee of the Special Tribunal, which is envisaged in Article 5 of the Agreement. The Tribunal is the culmination of a process, which commenced in May 2023, when the CoE created a ‘Register of Damage Caused by the Aggression of the Russian Federation against Ukraine’ (Resolution CM/Res(2023)3). Behind it stood the so-called ‘Core Group on the Establishment of a Special Tribunal for the Crime of Aggression against Ukraine’. Comprising legal experts from 37 states as well as representatives from the CoE and the EU, it was convened to consider Russia’s accountability solely for the crime of aggression. Later on, the ‘International Centre for the Prosecution of the Crime of Aggression against Ukraine’ was set up. It was located in The Hague, no doubt promoting the city’s status as the legal capital of the world.

According to Article 1 of the Agreement, repeated in Article 1 of the Statute, the Special Tribunal was created ‘to investigate, prosecute and try persons who bear the greatest responsibility for the crime of aggression against Ukraine’. According to the Preamble, given that in the case of Ukraine the ICC cannot examine the crime of aggression due to jurisdictional limitations, the Tribunal will fill this gap. The Preamble goes on to say that, as a collaborative effort, the Tribunal is the most suitable solution to determine criminal accountability regarding those individuals bearing the greatest responsibility for the crime of aggression. Finally, the tribunal will avoid duplication of prosecutions at national (Ukrainian) level against the same individuals and ensures that it complies with the ne bis in idem principle. The latter is envisaged in Article 4 of Protocol 7 to the European Convention of Human Rights (1984) and was included in Article 17 of the Statute. As regards that the Tribunal is complementary to Ukraine’s criminal jurisdiction, this reflects the ICC’s principle of complementarity which is laid down in Article 1 of the Rome Statute. However, it is not clear from the Agreement whether the term ‘persons’ covers only natural persons (individuals) or legal persons (organisations) as well. This is not a rhetorical question: the notion of ‘criminal organisation’ was enshrined in Articles 9 et seq. of the Charter of the International Military Tribunal and it featured prominently in the Nuremberg Trials, where the crime of aggression was prosecuted for the first time.

Furthermore, Article 1 does not appear to delineate the ‘crime of aggression against Ukraine’ ratione temporis. Thus, did it start in February 2022 or does it go back to 2014 (annexation of Crimea)? Arguably, this is an important question because most European states as well as the EU regard the ‘special military operation’ as a continuation of the 2014 events. What also appears to have been left open is whether those investigated / prosecuted / tried for aggression could be nationals of any State or only of the aggressor state. A recent article published in International Law Blog argued in favour of the former suggestion. Interestingly enough, the CoE’s Q&A on the Tribunal talks only about ‘bringing Russian leaders to trial’ (Question 13).  Finally, there is the question whether Ukrainian nationals come under the Tribunal’s jurisdiction or whether their cases would be reserved for the domestic courts.

III. The legal basis of the Agreement

So far, the Agreement appears to be the only treaty concluded between the CoE and a Member State, other of course from the Special Agreement with France relating to the Seat of the Council of Europe (ETS No. 3, 1949), the legal basis here being Articles 11 and 40 of the CoE Statute (1949). The legal basis for concluding the Agreement is not stated therein and, therefore, it should be a matter for discussion. To that end, reference should be made to the General Agreement on Privileges and Immunities of the Council of Europe (ETS No. 2, 1949): while it provides that the CoE possesses juridical personality (covering the gap in the Statute which is silent on this matter), it does not give to the CoE the power to conclude agreements / treaties by itself and in its own name. On the other hand, it could be argued that the CoE possesses broad treaty-making powers, as evidenced by the over two hundred so-called ‘Council of Europe treaties’ that have been concluded until today (all available at the CoE Treaty Office). However, the legal basis for these treaties is set out in Article 1(b) in conjunction with Article 15 of the CoE Statute. Significantly, they have a totally different purpose and content, namely to propose ‘agreements and common action in economic, social, cultural, scientific, legal and administrative matters’ to be adopted by all Member States. As has been argued, these treaties are not CoE legal instruments as such but are concluded because Member States have given their consent and subsequently ratified them. To that extent, Committee of Ministers Resolution (51) 30 B of 3 May 1951 lays down the relevant procedure: agreements/treaties are submitted to all Member States for ratification and shall be binding only to those members that ratified them. It should be noted that the Tribunal Agreement has not appeared in the CoE Treaty Office list and, therefore, it should not be considered as part of the ‘Council of Europe Treaty Series’. 

Another related matter, is the entry into force clause, Article 9 of the Agreement. It provides that three conditions must have been met: (a) the Agreement has been signed by the Secretary General (SG) expressing the CoE’s consent to be bound by it; (b) Ukraine has notified the CoE in writing that the ratification process (presumably this would be Article 85(32) of the Constitution) has been completed; and (c) the aforementioned Enlarged Partial Agreement has been established. It is not clear in which capacity did the SG sign the Agreement, since the Statute does not designate him/her as the CoE’s legal representative; under the General Agreement on Privileges and Immunities, he/she may only act on behalf of the CoE in order to sign contracts, to acquire/dispose of property and to institute legal proceedings. Presumably he was so authorized by the Committee of Ministers, the organ in which all Member States are represented. However, the question of the CoE’s legal representation persists. Take for example Article 8 of the Agreement, the settlement of disputes clause (disputes between the two parties concerning its interpretation or application shall be settled by negotiation or any other mutually agreed manner). Who and pursuant to which procedure will represent the CoE in such an eventuality?   

IV. The Enlarged Partial Agreement and the Management Committee

The fact that the CoE Member States (expect of course Ukraine) are not involved in the operation of the Tribunal was probably the reason why the drafters created a Management Committee. If one wanted to describe it, one could say that it is like the Conferences of Parties which are established by multilateral treaties. The modalities and criteria for membership of the Management Committee are not laid down in the Agreement but will be determined by the aforementioned Enlarged Partial Agreement. According to Article 5 of the Agreement, the Committee will be established within the CoE’s ‘institutional framework’ to finance the Special Tribunal and to carry out the administrative and managerial functions set out in its Statute. Space does not allow a detailed discussion of the Enlarged Partial Agreement, a kind of instrument to be found only in the CoE. Suffice to mention that it is not an international treaty, only a specific form of co-operation within the CoE, to which, however, not all Member States must agree. On the contrary, non-Member States and intergovernmental organisations may participate. A relevant example is Council Decision (EU) 2024/2045 of 22 July 2024 on the position to be taken on behalf of the Union within the Council of Europe bodies as regards the status of the European Union in the Enlarged Partial Agreement on the Register of Damage caused by the Aggression of the Russian Federation against Ukraine.

V. Conclusions

The Criminal Tribunal appears to constitute another type of entity in international criminal justice, whereby an international organisation creates a tribunal to adjudicate specifically aggression by one Member State against another Member State.  One wonders if such a tribunal with this jurisdiction could have been established by the UN, acting through the General Assembly and with Article 22 of the Charter as the legal basis. It is too early to have an informed opinion about the Tribunal.  Notwithstanding questions about the real value of such a tribunal, questions regarding the possibility of those accused ever being tried in person before it, the rapport between it and the ICC, etc., there is arguably another dimension: will the CoE consider creating such criminal tribunals for prosecuting those most responsible for acts of past aggression?  This is not a rhetorical question: in the European Court of Human Rights’ Grand Chamber judgment of 12 May 2014 in Cyprus v Turkey, a judge said that this case was the most important contribution to peace in Europe in the Court’s history and that the message to Member States was clear: if they wage war, invade or support foreign armed intervention in another Member State, they must pay for their unlawful actions and their consequences.[1]

[1] ECtHR, Cyprus v Turkey, Application No. 25781/94, Judgment (Just Satisfaction), 12 May 2014. See the concurring opinion of Judge Pinto de Albuquerque, joined by Judge Vučinić at 24.