Critical international legal analysis of the Agreement between the Council of Europe and Ukraine on the establishment of a Special Tribunal for the crime of aggression against Ukraine

This article provides a critical international legal analysis of the Agreement on the Establishment of a Special Tribunal for the Crime of Aggression against Ukraine, concluded on June 25, 2025, between Ukraine and the Council of Europe. The study focuses on the validity of this agreement, establishing the fact of abuse of power by the Council of Europe's principal organs, and challenging the legitimacy of a new model for creating an international criminal justice body. The study is based on an analysis of the scholarly works of Russian and foreign scholars in the field of international and criminal law. The author also analyzes the 1949 Statute of the Council of Europe, the 1969 Vienna Convention on the Law of Treaties, the 2025 Agreement on the Establishment of a Special Tribunal, and legal foundations for the establishment of temporary international criminal justice bodies. The methodological basis of the study was formed by general scientific (comparison, analysis, synthesis, analogy, deduction, induction, and others) and special (formal logic, legal interpretation, and others), historical-legal, systemic, and other methods of inquiry. Considering that this topic has not been explored in domestic research, the article may serve as a doctrinal basis for further discussions and the development of a conceptual, theoretical, and legal framework for developing counterarguments to the illegitimate decisions adopted by the Council of Europe and Ukraine. The research substantiates the lack of legitimacy of the Council of Europe to establish a temporary international criminal justice institution, including when applying the concept of implied competence of international organizations. The author's arguments allow for a critical assessment of the legality of establishing an international criminal justice institution based on agreements between a state and an international regional organization with competence in the field of human rights protection. The author refuted the possibility of raising the issue of classifying acts of aggression in state actions and the issue of immunities for state officials to the level of an international regional organization, ignoring the UN Security Council. The study's results can be applied in research and educational activities, and may also be of practical use to the competent authorities of the Russian Federation defending Russia's interests in the international arena.