This year marks the 80th anniversary of the U.N. Charter, conceived as the constitutional framework of the international community. At the time of its ratification, the Charter reflected the aspirational goals of a world yearning for peace and security in the aftermath of the Second World War. Article 2 of the Charter lays down a foundational pillar: the prohibition of “the threat or use of force against the territorial integrity or political independence of any state.” This principle underpins the crime of aggression – a crime committed by Russia’s leadership first in 2014 and again with its full-scale invasion of Ukraine on Feb. 24, 2022.
For more than three years, efforts have been underway to establish a Special Tribunal for the Crime of Aggression against Ukraine, aimed at holding Russia’s leadership accountable. In January 2023, a Core Group of approximately 40 countries – including Ukraine, members of the Council of Europe, the European Union, and other supporting nations – spearheaded this initiative. This breadth of support underscores the principle that accountability for the crime of aggression transcends national interests. From March 19 to 21 of this year, the Core Group convened in Strasbourg, France, to finalize the Tribunal’s Statute – its 14th and most consequential to date. With the technical legal framework now completed, the process moves into the political stage, requiring formal approval of the Agreement between Ukraine and the Council of Europe.
The Tribunal’s proposed legal and operational structure has undergone multiple revisions. Political disagreements among participating States – compounded by the Trump administration’s complete withdrawal from the process – have complicated progress. As a result, not all parties are fully satisfied with the final compromises.
One of the most contentious issues during negotiations was whether head of State immunity (i.e., ratione personae) should be recognized. Under customary international law, sitting heads of State are typically shielded from prosecution in foreign national courts. However, this type of immunity does not extend to international criminal tribunals – such as one created by the U.N. Security Council, authorised by a U.N. General Assembly resolution, or constituted through multilateral treaties such as the Rome Statute of the International Criminal Court. Many Core Group states, particularly the Baltic countries, argued that the proposed Tribunal, backed by the Council of Europe and open to broader international participation, meets the threshold and could, therefore, reject head of State immunity. However, G7 nations retained their opposition to this position, fearing it would set a precedent for future ad hoc tribunals to target sitting heads of State, heads of government, and foreign ministers – the so-called “Troika.”
In the end, a compromise view won out, limiting but not fully abolishing personal immunity. Under the framework, official status would not protect individuals from investigations. The Tribunal’s Prosecutor would be able to prepare indictments against those in positions of authority who plan, prepare, initiate, or execute acts of aggression – namely senior political and military leaders. However, for members of the Troika, an indictment could not be confirmed while they remain in office. No arrest warrant would be issued in such cases, and the pre-trial judge would be required to suspend proceedings until the individual leaves their position. As a result, the proposed Tribunal framework stops short of fully abolishing personal immunity.
Another central point is whether the Tribunal will allow trials in absentia. While such trials are generally prohibited in common law jurisdictions, they are permitted in many civil law systems, including Ukraine. The Core Group ultimately agreed that trials in absentia could proceed if an indicted individual failed to appear. However, the rights of the accused would be safeguarded, including the appointment of defense counsel and the right to a retrial upon their return. Yet here, too, a significant limitation remains: members of the Troika would not be allowed to be tried in absentia. This means that as long as Vladimir Putin remains in office, he would not face trial – only the possibility of indictment.
Initial discussions envisioned a jurisdictional framework grounded in broader international authority. However, the final arrangement ties the Tribunal’s jurisdiction exclusively to Ukraine’s territorial sovereignty. Only the Ukrainian Prosecutor General can submit information or evidence to the Tribunal. Furthermore, only Ukraine can request the Tribunal to investigate and, where appropriate, prosecute a specific individual for the crime of aggression.
Although the proposed Special Tribunal for the Crime of Aggression against Ukraine is a product of compromise and is far from perfect, it represents a vital mechanism for upholding the post-Second World War international legal order. States must now show the political will to implement it without delay. The Tribunal cannot be treated as a bargaining chip in negotiations to end hostilities. To do so would undermine the principle of accountability and inflict lasting damage on the international legal system. Failure to act now risks normalizing Russia’s blatant violations of territorial sovereignty – and rendering Article 2 of the U.N. Charter effectively obsolete.