Why Creating a Special Tribunal for Aggression Against Ukraine is the Best Available Option: A Reply to Kevin Jon Heller and Other Critics

Why Creating a Special Tribunal for Aggression Against Ukraine is the Best Available Option: A Reply to Kevin Jon Heller and Other Critics

[Dr Carrie McDougall, Melbourne Law School, University of Melbourne, is author of The Crime of Aggression under the Rome Statute of the International Criminal Court (2nd ed 2021, Cambridge University Press) and was involved in the Special Working Group on the Crime of Aggression and ICC Assembly of States Parties’ negotiations in relation to the crime of aggression.]

This post is a reply to the post published by Opinio Juris’ own Kevin Jon Heller and others who have criticised the proposed establishment of a Special Tribunal for Aggression against Ukraine. Below I will explain both why it is critical that those individuals responsible for Russia’s (and Belarus’) acts of aggression against Ukraine be held to account, and why, in my view, an ad hoc tribunal is the best available option to do this. 

A Crime of Aggression Has Been Committed

It hopefully goes without saying that it is the role of a duly constituted, independent and impartial court of law to make determinations about guilt and innocence, after a defendant (represented by counsel of their choice) has had the opportunity to plead their case.

Nevertheless, in light of the overwhelming volume of publicly available evidence about both the actions of Russia and Belarus, and the role played by President Vladimir Putin and President Alexander Lukashenko in spearheading decisions to use force, the inescapable conclusion is that both have committed a crime of aggression (a crime under customary international law) in the invasion of, and ongoing use of force against, Ukraine. For those less familiar with the crime of aggression, I have briefly set out the reasoning that leads to this conclusion here.

Tom Dannenbaum writing for Just Security, has argued that a broader range of perpetrators could be prosecuted on the basis of the Nuremberg and Tokyo precedents. I agree that others in Russia and Belarus who meet the definition of a potential perpetrator found in Article 8bis(1) of the Rome Statute (‘a person in a position effectively to exercise control over or to direct the political or military action of a State’) should be investigated and, if warranted, prosecuted.

However, in my view, it is clear that the Rome Statute formulation narrows the definition of those capable of committing a crime of aggression compared to the class of persons captured by the Statutes of the IMT and IMTFE and prosecuted by those Tribunals, as explained in detail in my book on the crime of aggression (pp. 213-257). And, for reasons explained below, I think it is imperative that the constitutive instrument of any ad hoc mechanism established to prosecute crimes of aggression committed against Ukraine replicate the definition of the crime of aggression found in the Rome Statute.

The ICC Lacks Jurisdiction – and There’s No Easy Fix to Remedy This

It was exceedingly difficult for International Criminal Court (ICC) States Parties to reach agreement on the definition of the crime of aggression. Ultimately, however, the real fight was over the scope of the ICC’s jurisdiction over the crime. The result is a unique regime that governs the ICC’s jurisdiction over the crime of aggression, which gives the Court jurisdiction in a narrower range of situations compared to other Rome Statute crimes – an outcome insisted upon by the P5 and reluctantly accepted by other States as the price paid for reaching agreement on aggression.

The jurisdictional provisions are complex, and their interpretation remains contested. As such, much could be said about them and their flaws – indeed, I devote some 40,000 words to these issues in the latest edition of my book. For present purposes, however, we can put much of the complexity and unresolved debates to one side. For it is clear that, in the absence of a UN Security Council referral, the ICC is not able to exercise jurisdiction over a crime of aggression involving a non-State Party (such as Russia, Belarus and Ukraine), as either aggressor or victim State, as a result of a comprehensive non-State Party carve out included in Article 15bis (5).

As such, even if Ukraine takes the step of building on its ad hoc declarations accepting the ICC’s jurisdiction under Article 12(3) and ratifies the Rome Statute and the aggression amendments, the ICC will lack jurisdiction over the crime of aggression committed by Putin and Lukashenko.  

For completeness, I would also note that in my view it is not possible for a State to enliven the jurisdiction of the Court over aggression through an Article 12(3) declaration absent its ratification of the Rome Statute because Article 15bis (5) must be viewed as lex specialis. This interpretation is confirmed by resort to the travaux préparatoires, which record the fact that a draft interpretive ‘understanding’ that would have contemplated the use of Article 12(3) was taken off the table after a number of States Parties expressed concern that an ability of non-States Parties to accept the jurisdiction of the Court on an ad hoc basis would unfairly advantage such States, which would be able to decide after the fact whether to allow the Court to investigate a crime of aggression or not.

It has been suggested that the Rome Statute should be amended to enable the General Assembly to refer situations to the ICC and enliven the Court’s jurisdiction over the crime of aggression committed against Ukraine in order to get around the problem of the veto. However, under Articles 10, 11, 12 and 14 of the UN Charter, the GA’s powers are limited to making recommendations: as confirmed by the International Court of Justice in the Certain Expenses Case (p. 165), the GA lacks the ability to take coercive or enforcement action, which is the exclusive prerogative of the UNSC. And as the ICTY Appeals Chamber made clear in the Tadic Jurisdiction Decision ([37]-[40], [44]), the establishment of a criminal tribunal (i.e. the creation of compulsory criminal jurisdiction) is a form of such coercive or enforcement action. As such, while the GA could take steps to support an exercise of criminal jurisdiction possessed by one or more UN Member States (as discussed further below), the GA lacks the power to create criminal jurisdiction where there would otherwise be none.

What would be ideal, in my view, is to amend the Rome Statute to apply the ICC’s ordinary jurisdictional regime set out in Article 12 to the crime of aggression. My hope is that current events will result in more States ratifying the Rome Statute and the aggression amendments, and supporting the review of the jurisdictional provisions in order to reinforce the prohibition of the use of force. However, having been at the coalface of aggression negotiations for almost 20 years, I think it is unlikely that States Parties will agree on amendments. In the happy event I’m proven wrong, it’s important to appreciate that under Article 121(4), change would require ratification of a new amendment by seven-eighths of States Parties – a target so high that one can discount this as a viable option for the prosecution of the crime of aggression committed against Ukraine, even assuming it would be possible to give the amendment retroactive effect.

For the foregoing reasons, while it is deeply regrettable, I don’t believe there is any viable option to enliven the ICC’s jurisdiction over the crime of aggression committed against Ukraine.

Any Domestic Proceeding Will Lack Legitimacy and Faces a Real Risk of Being Successfully Challenged By a Defendant

As I have explained here, at least 74 States have domestic aggression offences. Most of these States would, however, lack jurisdiction on the basis of present facts, given the scope of jurisdiction over such offences is in the majority of cases limited to scenarios where the forum State has been an aggressor or victim.

As others have noted, Ukraine has criminalised aggression under Article 437 of its Criminal Code, enjoys territorial jurisdiction, and has announced that it has opened an investigation.

Lithuania asserts universal jurisdiction over the crime of aggression (Articles 7 and 110) and has reportedly opened an investigation in relation to aggression and other crimes.

Poland asserts jurisdiction over aggression (Articles 112 and 117) that is more akin to the protective principle: it too has reportedly opened an investigation that extends to aggression.

While a number of commentators are championing such initiatives, in my view, any domestic prosecution would be difficult and suffer from a legitimacy deficit.

In the first place, an exercise of jurisdiction by a State other than Ukraine could potentially be successfully challenged. The fast pace of current events has precluded me from investigating whether there is any relevant Polish jurisprudence that would shed light on the operation of Article 112 of its Criminal Code, but, on its face, it’s not obvious to me that the crime of aggression committed against Ukraine is ‘an offence against the internal or external security of the Republic of Poland’ (or even ‘an offence against essential economic interests of Poland’).

There is also a possibility of any exercise of universal jurisdiction over the crime of aggression being challenged. At least 18 States assume universal jurisdiction over the crime of aggression. In Pinochet, Lord Millet (at [34]) held that crimes against peace attract universal jurisdiction, a conclusion that is consistent with Principle 2 of the Princeton Principles of University Jurisdiction. Scholars, however, are divided over the issue, and crimes against peace/the crime of aggression is more often than not absent from the list of crimes said to attract universal jurisdiction in leading commentaries. Notably in this regard, none of the separate judgments in the ICJ Arrest Warrant Case that attempt to identify the crimes to which universal jurisdiction attaches includes the crime of aggression or crimes against peace. As former legal adviser at Australia’s Mission to the UN in New York I was heavily engaged in discussions on the universal jurisdiction agenda item of the Sixth Committee, and I can attest to the fact that in my engagement with a very significant number, and broad cross-section, of Member States on their views on universal jurisdiction, only a handful suggested that universal jurisdiction attaches to crimes against peace/the crime of aggression, a position that accords with views expressed in the annual debate on the topic.

Second, a defendant might be able to successfully avoid prosecution before any domestic court on the basis that he or she enjoys immunity under international law. While it has attracted criticism, the judgment of the ICJ in the Arrest Warrant Case is a strong statement that Heads of State, diplomatic representatives, ministers of foreign affairs and (by implication) Heads of Government, enjoy immunity from criminal proceedings in foreign domestic jurisdictions during their term in office for both ‘official’ and ‘private’ acts, committed during, or prior to, that term in office, even when accused of serious international crimes (at [54]-[55]). According to the majority, once leaving office, such persons can be prosecuted before national courts for acts committed prior or subsequently to his or her term in office, and acts committed in a private capacity during his or her period in office (at [61]).

Some commentators suggest that the judgment leaves room to conclude that war crimes and crimes against humanity should not be regarded as official acts. It is difficult, however, to accept that this argument can be extended to the crime of aggression given it is a stretch to claim that a use of force authorised by the leader(s) of a State is not an ‘official act’, when by definition the State act element of the crime would attract State responsibility. It has alternatively been argued that there is a customary law exception to functional immunity for serious international crimes regardless of whether they are committed in an official capacity. Support for this view can be found in the report of the International Law Commission Special Rapporteur’s Fifth Report on Immunity of State Officials from Foreign Criminal Jurisdiction. But while the ILC has provisionally concluded that immunity ratione materiae from the exercise of criminal jurisdiction does not apply to certain international crimes, aggression is not included in that list (draft Article 7).

In summary, it is in my view clear that foreign domestic courts will be unable to exercise jurisdiction over persons who enjoy personal immunity (including Putin and Lukashenko) during their term in office. It is more difficult to be definitive in relation to the current status of functional immunity under international law, but it is at least questionable whether a foreign domestic court could lawfully exercise jurisdiction over State officials for crimes of aggression committed as part of a State’s sanctioned foreign or military policy. And I’d argue that this is not a question that we would want to hang over a future trial of those responsible for Russia’s (and Belarus’) acts of aggression.

Third, domestic jurisdictions are unlikely to be able to secure Putin’s and Lukashenko’s presence absent the cooperation of future Russian and Belorussian authorities. While trials in absentia are permitted in some jurisdictions (including Ukraine) they plainly lack the credibility of a proceeding in which a defendant has participated. An outstanding domestic arrest warrant may pose some inconvenience, but it wouldn’t have the same limiting effect as an arrest warrant issued by an international tribunal, not least because a target such as Putin or Lukashenko would potentially be immune from extradition processes for the reasons set out above.

Fourth, any domestic proceeding will struggle to escape the taint of victor’s justice or, as the case may be, victim’s revenge. Even if a Ukrainian proceeding received overt international support, Ukrainian authorities are unlikely to be perceived as acting in a wholly impartial manner.

Finally, I would argue that even though current events are a textbook example of the crime, it is not desirable to have national courts that lack the necessary expertise interpreting the jus ad bellum. This is in some ways demonstrated by the 2016 decision of the Golosyyvsky District Court of Kyiv in relation to former two Russian soldiers convicted of waging a war of aggression in the context of Russia’s earlier invasion of Crimea, without any reasoning being included that linked the acts of the accused to the actions of Russia, as described by Sergey Sayapin.

As such, in my view, it is with good reason that the International Law Commission, among others, has in the past recommended that aggression only be prosecuted on the international plane.

An Ad-Hoc International Tribunal is Both Legally Possible And Politically Desirable

Two principal models for an ad hoc international tribunal have been identified.

As first suggested by Larry M. Johnson, a tribunal could be recommended by the GA, created through an agreement between Ukraine and the UN, and approved by the GA, based on the precedent of the Extraordinary Chambers in the Courts of Cambodia or the Special Court for Sierra Leone. Such a tribunal would exercise Ukraine’s territorial jurisdiction over the crime, which exists under customary international law, and would presumably provide roles for international judges and staff in order to try to overcome perceptions of bias.

As argued by Jennifer Trahan, the obvious advantage of such a tribunal would be the legitimacy gloss provided by an endorsement of UN Member States. Trahan’s argument, however, is premised on the very significant assumption that an overwhelming endorsement could be secured. I don’t think we can extrapolate from the emphatic vote in favour of the GA resolution on Aggression against Ukraine, which attracted just five ‘no’ votes, that a similar level of support for an aggression tribunal would be forthcoming. My assessment would be that many States would view the creation of a hybrid tribunal to prosecute the leaders of another State for aggression as a very different prospect from supporting a State to prosecute its own nationals for war crimes, crimes against humanity or genocide. Any effort to go down this path would thus require extensive consultation among Member States to determine whether a strong outcome could be secured, lest efforts to hold Putin and Lukashenko to account, and to strengthen the prohibition of the use of force, be set backwards.

The alternative would be a tribunal established by international treaty, as first suggested by Philippe Sands (as elaborated by him here), now endorsed in a Statement and Declaration by a growing number, and supported by Ukraine, as made clear by the Ukrainian Foreign Minister in an event hosted by Chatham House.

The Declaration is somewhat vague as to the precise legal basis envisaged, referring to a ‘grant of jurisdiction arising under national criminal codes and general international law’. While I have reservations about whether the crime properly attracts universal jurisdiction as outlined above, as long as any treaty includes a delegation of Ukrainian territorial jurisdiction, there would be a sound legal basis for the prosecution of a crime under customary international law.

Advantages of this model would include that it may (at least to a degree) help shelter Ukraine from Russian retaliation, and if the treaty parties included at least two EU Member States it could take advantage of the EU’s Joint Investigative Team’s mechanisms and resources (which played a hugely important role in the investigation of the downing of MH17). Depending on the States ultimately prepared to join such a treaty, it is possible that it could also represent a significant percentage of the international community and a broad cross-section of States and thus enhance perceptions of legitimacy.

There is a good argument to be made that either model is at least potentially capable of being sufficiently international in nature to exclude the applicability of immunities for a prosecution of a serious international crime, in line with the decisions of the SCSL in relation to Charles Taylor, the ICC Appeals Chamber in relation to Omar Al-Bashir, and consistent with the comments on the ICJ in the Arrest Warrants Case which recognised that an incumbent immunity holder ‘may be subject to criminal proceedings before certain international criminal courts, where they have jurisdiction’ (at [61]). As reasoned by Dannenbaum, while the conclusion that no one enjoys immunity before an international court for serious international crimes under customary international law remains somewhat controversial, ‘the very fact of its repeated assertion by international authorities gives it weight’.

Sergey Vasiliev has argued that an ad hoc international tribunal would be unable to secure the presence of Putin or his co-accused in the absence of full Russian cooperation. In the event of Putin leaving power, Vasiliev argues that the need for an ad hoc mechanism would be rendered moot as new Russian authorities could ratify the Rome Statute and the aggression amendments. Heller also raises the possibility of a domestic Russian prosecution. However, in my assessment, even if current events lead to regime change in Russia, it is highly unlikely that the Russian Federation would ratify the Rome Statute and the aggression amendments and back date its acceptance of the jurisdiction of the Court, as Russia’s objections to the ICC, as voiced in the UNSC and other fora over the years, extend to concerns that go well beyond aggression. In realpolitik terms, there is also a significant difference between attempting to rehabilitate a country’s reputation by scapegoating a deposed leader and signing up to have all future crimes committed on one’s territory or by one’s nationals adjudicated on by the ICC. While we can only speculate about the shape of any future Russia, I would be willing to bet that cooperation with a limited jurisdiction ad hoc tribunal is much more likely to be forthcoming than cooperation with the ICC, or any foreign domestic authorities. I also think it more likely than not that a domestic Russian prosecution might not be the favoured option both because it could be assessed as providing insufficient rehabilitative value, but also because it could be more difficult to justify the limitation of liability to a select few, which, based on past precedent, would likely be possible as part of a deal to cooperate with an international tribunal. 

In the absence of full Russian cooperation, the issuance of an arrest warrant, able to be executed by multiple States, would severely limit Putin’s ability to engage on the international stage.

Trivial criticisms such as those relating to the potential cost of the tribunal should be readily dismissed. The financial cost of the current crisis is going to be of an almost unimaginable magnitude. If the international community cannot find the modest amount that would be required to establish and fund a limited jurisdiction tribunal to hold those responsible to account, in an attempt to prevent a repetition of current events, especially when compared to the amount currently being spent to arm Ukraine and to put financial pressure on Russia, then something about our priorities is very wrong indeed.

The principal criticism of the ad hoc proposal is that it would represent an egregious example of selective justice, which would undermine the international criminal justice project. This argument has several variations: that past crimes of aggression have gone unpunished; that in the future others will remain beyond the reach of the law; that it is unnecessary to establish a second tribunal to prosecute persons who could likely be prosecuted by the ICC for war crimes and crimes against humanity; that it would be inappropriate to establish a second international criminal tribunal to provide justice for crimes committed in Ukraine when the plight of victims of serious international crimes committed in places such as Syria and Yemen have largely been ignored.

In some quarters there has been a related assertion that double standards would come into play – an argument that seems to proceed on an assumption that those primarily responsible for neutering the ICC’s jurisdiction over aggression would be the first to lend their support to an ad hoc tribunal aimed at prosecuting Putin. Having seen first-hand the strength of US, UK and French opposition to the exercise of ICC jurisdiction over aggression, I would myself be surprised if they became party to such a treaty, not so much for fear of accusations of hypocrisy, but out of concern of the precedent that such a tribunal could represent. But even if the initiative is led by other States, this would not in and of itself address selectivity concerns.

I understand those concerns. But I don’t see the advantage of standing on principle and letting perfect be the enemy of good. I think we can acknowledge that justice is currently selective and advocate for better outcomes in the future, while pursuing what justice is within our grasp.

More specifically, this is the first clear-cut case of a crime of aggression since the adoption of an internationally agreed definition of the crime.

While there would seemingly be a strong basis to suggest that the ICC will be able to prosecute Putin for war crimes and crimes against humanity, cases before the ICC to date have demonstrated that tying puppet masters to crimes in the field is not a straight-forward task, noting that to date efforts have been directed against defendants who would not be able to marshall the same resources to which the likes of Putin would have access.

More importantly, in my opinion, a prosecution for war crimes or crimes against humanity (while definitely important and something to be pursued) is not a substitution for the prosecution of the crime of aggression. The magnitude and manifest nature of Russia’s (and Belarus’) violation of the prohibition of the use of force requires that those responsible be held to account. This is a wrong committed not only against civilians in Ukraine, but also against non-civilian Ukrainians who are lawful targets under international humanitarian war, and against the members of the aggressors’ armed forces being forced to fight a war on false premises. It is an action that has rendered Ukraine’s sovereignty asunder and threatened its very existence. It is also an unprecedented attack on the international order.

I could not disagree more strongly with Heller’s assertion that in light of the emphatic GA vote deploring Russia’s act of aggression, ‘it is not necessary to affirm the unacceptability and criminality of aggression.’ A condemnatory GA resolution is a slap on the wrist compared to the prosecution and punishment of the persons responsible for that aggression. Letting this crime go unpunished would represent a woeful failure to ensure that Putin and his allies are punished for the entirety of their wrong and to take all available steps to reinforce the prohibition of the use of force in order to do what we can to make sure that current events are repeated never again.

Recommendations to Help Ensure the Tribunal Strengthens the International Criminal Justice Project

Finally, there are a number of steps that I would recommend be undertaken to ensure that the tribunal is as robust as possible, and to help maximise its contribution to the longer-term international criminal project, as summarised briefly below:

  • A UNSC resolution seeking referral of the situation in Ukraine to the ICC should be put to a vote, notwithstanding its likely veto by Russia, in order to demonstrate that all possible avenues to get to the ICC have been exhausted;
  • The constitutive instrument of an ad hoc tribunal should replicate the definition of the crime of aggression found in Article 8bis of the Rome Statute to ensure that provision is not undermined;
  • The tribunal’s jurisdiction should be limited to the crime of aggression and the situation in Ukraine (or any other countries against which Russia and Belarus may end up using force) in order not to undermine the ICC;
  • A broad cross-section of States should be encouraged to join the treaty in order to underscore the international nature of the effort to prosecute those responsible for Russia’s (and Belarus’) acts of aggression against Ukraine, an effort that would ideally be led by Ukraine’s closest neighbours;
  • Renewed efforts should be made to encourage all States, but especially those supporting the tribunal, to ratify the Rome Statute and the aggression amendments in order to reduce the scope for complaints to be made about hypocrisy, to strengthen the deterrent effect of the crime, and to underscore States’ commitment to the prohibition of the use of force; and
  • An agreement should be concluded between the ad hoc tribunal and the ICC to emphasise their joint justice project and to deal with practical matters such as the sharing of evidence, and the sequencing of any trials of individuals wanted for prosecution by both institutions.


While sceptics have suggested that Russia’s actions have signalled the death of Article 2(4), I would instead argue that the unprecedented response by the international community to the violation of the prohibition of the use of force, and the international community’s reliance on international law in doing so, proves that the overwhelming majority of States consider Article 2(4) to be the keystone of the international order. Prosecuting Putin and other leaders for the crime they have committed, and ratifying the aggression amendments, would underscore that such violations will not be tolerated and thus help to ensure that those who might seek to emulate Putin’s actions are stopped in their tracks.

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Patrycja Grzebyk
Patrycja Grzebyk

In case of Russia let’s do not forget that Russia (as well as e.g. Poland and Lithuania) can rely not only on customary law but also on London Conventions of 1933 defining aggression. Concerning Polish provisions, indeed Prosecution decided to use protective jurisdiction (article 110) but this is due to the fact that article 117 which criminalizes war of aggression is constructed in very general way and it is interpreted as aiming at protection of international security system which UN Charter is the basis. So the construction of article 117 is not to protect territorial integrity of Poland as such, but to protect international peace, in other words any aggression endangers world peace and thus security of Poland. I think this is also safer solution than universal jurisdiction (because of the mentioned by author arguments). In addition, it is disputable whether national provisions need to limit criminalisation of aggression only to leaders (ICC has also limited jurisdiction over war crimes which does not mean that isolated war crimes cannot be prosecuted in national courts; so similar thinking could be applied to crime of aggression). I am not big fan of prosecution of aggression (I would prefer to focus on CAH… Read more »