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This briefing updates and supersedes research from the Common’s Library Debate Pack relating to the proposed Special Tribunal (5 May 2023), and updates developments originally covered in the Commons Library Briefing Paper Ukraine crisis: Recognition, military action, and international law (24 March 2022).

Russia’s 2022 invasion of Ukraine and Aggression

Proposals for a Special Tribunal for Ukraine relate directly to the specific crime of aggression, and is separate to international investigations ongoing by the International Criminal Court relating to alleged war crimes and other international crimes that may have been committed following Russia’s invasion of Ukraine.

After Russia invaded Ukraine on 24 February 2022, some states were quick to label this as an act of aggression in their immediate reactions. On 2 March 2022 the UN General Assembly passed a Resolution titled “Aggression against Ukraine”. Among other statements, it said that the General Assembly “Deplores in the strongest terms the aggression by the Russian Federation against Ukraine in violation of Article 2 (4) of the Charter.”

What is Aggression in international law?

Aggression is an international crime in international law. It is closely related to the prohibition of force in international law under Article 2(4) of the UN Charter, but aggression is a crime with specific criteria. This briefing outlines the definition of aggression, as agreed by the UN General Assembly in 1974. The General Assembly declared in Article 1 of the definition what aggression is and lists some of the acts that could amount to aggression as including:

  • Invasion, occupation, or annexation of another state’s territory.
  • Bombardment of another state’s territory.
  • Blockades of ports or coasts.
  • Attacks by one armed force against another.
  • In situations where there is an agreement between two states that provides for the presence of forces within the territory of the receiving state. A use of force in contravention of the conditions provided for in the agreement or any extension of their presence in such territory beyond the termination of the agreement.
  • Allowing a state’s own territory to be used to launch such attacks by another state against a third state.
  • The sending by or on behalf of a state of armed bands, groups, irregulars or mercenaries, which carry out armed acts of such gravity as to amount to the acts listed above, or its substantial involvement therein.

Proposals for a Special Tribunal

The International Criminal Court (ICC) cannot exercise jurisdiction over the crime of aggression unless both the victim and the aggressor state has ratified and accepted the Court’s jurisdiction over that crime, or where the UN Security Council refers the situation to the Court. Neither Russia nor Ukraine are parties to the Rome Statute, and Russia is able to veto any decision at the UN Security Council.

Ukraine did submit a declaration in 2015 to accept the jurisdiction of the Court over any acts of genocide, crimes against humanity or war crimes that may be committed within the territory of Ukraine since 20 February 2014 onwards. However, the Prosecutor of the ICC has noted that this does not apply to the crime of aggression, and that the crime of aggression cannot apply to the current situation in Ukraine.

Because the ICC does not have jurisdiction over the crime of aggression in Ukraine, a number of politicians and experts signed a combined statement and declaration calling for a “Special Tribunal for the punishment of the crime of aggression against Ukraine”.

Possible forms of a Special Tribunal and legal issues

There are a number of different avenues to establishing an international tribunal to prosecute aggression, and the most suitable and legally-sound avenue to establishing this is the subject of ongoing considerable debate among experts.

Based on the commentary cited in this briefing, some of the main routes being considered to create such a Special Tribunal are outlined. However, not all of these options are considered legally viable. Each of the options outlined have specific and complex legal obstacles, as well as political and practical issues that may need to be addressed.

  • Option 1 – Amending the International Criminal Court’s Rome Statute to allow referrals by the UN General Assembly to prosecute aggression.
    • Commentary suggests this seems unlikely to be workable, given the numbers of ICC member states who still have not submitted to the Court’s jurisdiction over aggression themselves.
  • Option 2 – A Ukrainian court established with international support (the hybrid model).
    • This would involve Ukraine having jurisdiction over the crime of aggression, but applying international crimes to prosecute, possibly involving both Ukrainian and international judges and prosecutors from another international organisation.
    • However, there may be restrictions in Ukraine’s constitutionon setting up such a hybrid court, depending on its form.
  • Option 3 – an international court established by the UN General Assembly, with the agreement of Ukraine.
    • This would be a court set up through an agreement between the United Nations and Ukraine, endorsed by a General Assembly Resolution authorising the UN Secretary-General to set up such a mechanism. This could work similarly to the Special Court for Sierra Leone.
  • Option 4 – a treaty between interested states creating a Special Tribunal.
    • This would be an international agreement between like-minded states to prosecute aggression against Ukraine. But there are potential jurisdictional and immunity issues with this model, as well as a risk of the court being seen as politically selective.

Recent reports and comments also suggest a fifth option has been considered, including the hosting of a tribunal in a third state, but details on this and its precise legal basis are still to be made clear.

Other models are also possible, but not notably considered as yet.

The main issues to be considered in creating such a tribunal include:

  • On what basis the Special Tribunal would have jurisdiction
  • How the Special Tribunal would address the functional and personal immunities of members of Russia’s leadership
  • The resources available to the Special Tribunal, and how it would be funded

Commentators have also questioned whether a Special Tribunal on the Crime of Aggression would give rise to selective justice, because the crime of aggression has not been prosecute for any conflict since World War II. This issue is further explored in the briefing paper.

Support for a tribunal

Ukraine itself supports the creation of a Special Tribunal, and has been open to exploring the different legal avenues. Ukraine’s President Zelensky has called for the Tribunal. A ‘Core Group’ of 40 states has been established to discuss and develop the precise form of a special tribunal, and discussions are ongoing about how to proceed.

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