A New Court to Prosecute Russia’s Illegal War?
A New Court to Prosecute Russia’s Illegal War?
A view shows graves of Ukrainians killed in fighting amid Russia's attack on Ukraine, at a cemetery in Kharkiv, Ukraine. January 31, 2023. REUTERS / Vitalii Hnidvi
Q&A / Global 19 minutes

A New Court to Prosecute Russia’s Illegal War?

Russia’s all-out invasion of Ukraine has prompted discussion of how to hold top Kremlin officials accountable for this flagrant violation of international law. In this Q&A, Crisis Group examines the pros and cons of three main options that have been broached to date.

What is happening?

Soon after Russia launched its unlawful, full-scale invasion of Ukraine in February 2022, international lawyers, former government officials, scholars and others began advocating for the establishment of a new tribunal to prosecute the Russian leadership for the crime of aggression. As death and destruction from Russia’s war mounts, a core group of more than 30 states is discussing the creation of such a tribunal. Proponents argue that Russia’s all-out invasion is a grave international crime and a profound breach of the international order that must not go unpunished. They say meaningful accountability – which can be achieved only by punishing those who decided to wage the war – is necessary to affirm the prohibition of aggression and conquest under international law and to deter such wars in the future.

What is the crime of aggression? Why would a new tribunal be needed to prosecute the crime?

The crime of aggression is first and foremost a violation of international law’s prohibition of the use of force. Article 2(4) of the UN Charter proscribes the use of force, subject to narrow exceptions. The crime of aggression seeks to give this prohibition teeth by imposing criminal liability on individuals responsible for significant breaches of it. As discussed below, this crime was first recognised as part of customary international law by the International Military Tribunal at Nuremberg following World War II. The victorious allies who had just won the war established the Tribunal to try the defeated German leadership.

Following Nuremberg, the field of international criminal law was largely dormant for much of the Cold War, and it was five decades before the crime of aggression became a major focus of international attention again. The Rome Statute of the International Criminal Court (ICC), which was drafted in the 1990s, articulated the crime of aggression as a potential offence coming under the court’s jurisdiction, but because of surrounding controversy left the definition and activation of this offence for a later date.

Responsibility for the crime of aggression rests at the top of the chain of command.

The ICC state parties amended the Rome Statute to define the crime of aggression at the ICC’s 2010 review conference in Kampala, Uganda, and the amendments they agreed to there came into effect in 2018. The states agreed that the crime of aggression consists of planning, preparing, initiating or executing an “act of aggression” that, by its character, gravity and scale, “constitutes a manifest violation of the Charter of the United Nations”. The Kampala amendments specify that the offence covers – among other things – any invasion or attack by a state’s armed forces on the territory of another state, any resulting military occupation and any annexation of another state’s territory by the use of force. To make clear that responsibility for the crime of aggression rests at the top of the chain of command, they stipulated that it can only be committed by a person in a position to “control” or “direct” a state’s political or military activities.  

But the Kampala amendments to the Rome Statute include a major loophole. They provide that, for states that are not party to the Rome Statute, “the Court shall not exercise its jurisdiction over the crime of aggression when committed by that State’s nationals or on its territory”. This clause means that the ICC is expressly precluded from charging many of the world’s most powerful countries – including great powers like the U.S., China and Russia, as well as prominent middle powers like India, Israel, Saudi Arabia and Türkiye – with the crime of aggression, because they do not belong to it. Of course, the gap in the Court’s jurisdiction is no accident. In negotiations over the activation of the crime at Kampala, the U.S. worked behind the scenes to ensure that the Rome Statute amendments would not create any criminal exposure for U.S. personnel.

Thus, even though Ukraine has submitted to the ICC’s jurisdiction, albeit without becoming a state party, the Court’s reach there is limited to the non-aggression crimes within its writ. These include all of the crimes covered by the Rome Statute prior to 2018 – ie, war crimes, crimes against humanity and genocide. The Court has no jurisdiction over crimes of aggression committed by Russia (or other non-party states) in Ukraine or anywhere else. 

Is there any precedent for prosecuting the crime of aggression?

Precedents for prosecuting the crime of aggression are limited. The overwhelming majority of prior prosecutions are from the World War II era, following the defeat and occupation of Nazi Germany and imperial Japan. In Germany, as noted above, the allies created the International Military Tribunal at Nuremberg. The Tribunal was the primary forum where the allies prosecuted German political, military and economic leaders in connection with “crimes against the peace” – ie, the “planning, preparation, initiation and waging of wars of aggression”. A similarly named successor body, the Nuremberg Military Tribunal, subsequently tried German officials in the Ministries case. On the Asian front, Japanese leaders faced prosecution for crimes against the peace at the International Military Tribunal for the Far East, which the victorious allies established in Tokyo.

Beyond the post-World War II cases, international precedents are scant. The ad hoc international criminal tribunals created following the Cold War – eg, the courts created by the UN Security Council to try atrocities in the former Yugoslavia and Rwanda in the 1990s – lacked jurisdiction over the crime of aggression. As discussed above, the ICC expanded its jurisdiction to try the crime of aggression with effect as of 2018, but the prosecutor has never charged this offence. 

Domestic courts can also try the crime of aggression, though again examples are few and far between. Recent instances come from Ukraine, which has conducted domestic trials for the crime of aggression arising out of Russia’s 2014-2015 intervention. In 2019, a Ukrainian court convicted Ukraine’s former President Victor Yanukovych of “complicity in waging a war of aggression”. Because Yanukovych had fled to Russia in 2014 (where he remains to this day), Ukraine tried him in absentia.

What are the options for setting up a new tribunal to try the crime of aggression, and which ones do Ukraine and its partners prefer?

While the ICC lacks jurisdiction over the crime of aggression regarding Russia’s war in Ukraine, another court could conceivably prosecute the offense. For example, as with Yanukovych, Ukraine’s domestic courts could try individuals for the crime of aggression. But under international law, these courts would likely be required to recognise immunities for Russia’s heads of state and government, as well as its foreign minister. The same is true for other states that have criminalised aggression in their domestic law and might in principle be able to assert universal jurisdiction over alleged Russian perpetrators who at some point come to be present on their territory. Like Ukraine, these states would likely encounter immunity issues if they seek to prosecute Russia’s top leadership.  

Advocates for prosecuting the crime of aggression have therefore primarily focused on establishing a new tribunal that would be able to assert jurisdiction of all those responsible for the war up to President Vladimir Putin himself. Although many of these calls for a new tribunal have been vague on details, three primary models have emerged:

  • The first option would be a tribunal based on a multilateral treaty among Ukraine and a “coalition of the willing” states, styled after the International Military Tribunal at Nuremberg.
  • A second option would be to establish a tribunal based on an agreement between Ukraine and the UN, endorsed by a resolution from the UN General Assembly. Proponents cite as precedents tribunals established by agreements between the UN, on one side, and each of Sierra Leone and Cambodia, on the other.
  • The third option would be to create a special, hybrid chamber based on Ukrainian domestic law, but incorporating international elements.

There is not yet a uniform view among Ukraine and its Western partners about which of these options to support. Proponents of the first two options include the Baltic states, Poland and Belgium, as well as individuals like former UK Prime Minister Gordon Brown (who favours option one). They argue that the international courts envisaged would be able to pierce the absolute status-based immunities that Russia’s “troika” (head of state, head of government and foreign minister) would likely enjoy in even a hybrid domestic prosecution. Either of the first two options would allow the tribunal to go straight to the top of the Kremlin hierarchy.

A Ukraine-based initiative would be unable to go after the [Russian] troika while they remain in power, but ... there could be other targets.

As concerns the third option, its most vocal supporter to date has been Germany, but it appears to be gathering momentum with other key partners, if not with Ukraine itself. In addition to apparent backing from France, Italy and possibly the UK, the U.S. has announced its support for an “internationalised tribunal” along these lines. Proponents acknowledge that a Ukraine-based initiative would be unable to go after the troika while they remain in power, but believe there could be other targets – eg, members of the Russian Duma who voted in favour of the invasion and troika members who leave office. Kyiv, however, appears unenthusiastic about this approach. In a recent interview, Andrii Smyrnov, the deputy head of Ukraine’s Presidential Office, rejected the idea of a hybrid tribunal as unconstitutional (though whether it passes constitutional muster would likely depend on the level of international participation). He also suggested that anchoring such a tribunal in Ukraine’s justice system would create an impression that the crime of aggression is merely a bilateral dispute between Ukraine and Russia. 

The chances of any Russian official coming into the custody of any of these bodies in the foreseeable future are remote, so the major difference may be that an international court constituted under the first two options might theoretically try the troika in absentia, whereas a hybrid court created under the third option could not try them under any circumstances.

What are the potential benefits to establishing an aggression tribunal?

Proponents of a new tribunal tend to argue that the unique gravity of the crime of aggression requires focused attention. Former UK Prime Minister Brown has invoked the judgment of the International Military Tribunal at Nuremberg. The Nuremberg tribunal observed that the initiation of a war of aggression “is the supreme international crime differing only from other war crimes in that it contains within itself the accumulated evil of the whole”. Informed by this logic, the push to prosecute the crime of aggression will likely remain strong, regardless of how vigorously the ICC and other courts appear to be proceeding with efforts to prosecute atrocity crimes and whom they are targeting. (Indeed they are proceeding quite vigorously: in March, the ICC issued warrants for the arrest of President Putin and his children’s commissioner, Maria Lvova-Belova, for war crimes relating to the unlawful transfer and deportation of children.)  

Proponents of a new tribunal to prosecute the crime of aggression offer other arguments as well. They cite the need to uphold international law’s prohibition of the use of force in the face of Russia’s egregious violation. As noted, some advocates contend that prosecuting the Russian officials responsible for the conflict is necessary to deter future wars of aggression. The international lawyer Philippe Sands has argued that prosecuting Putin before an international tribunal would further delegitimise him, possibly creating an incentive for those in his inner circle to “peel off” or offering Ukraine and its partners leverage in future negotiations. Ukrainian officials also sometimes suggest that convicting Russian officials for the crime of aggression will aid Ukraine in its efforts to force Russia to pay reparations, potentially from Russian assets frozen abroad.

Are there divisions between the West and the so-called Global South when it comes to support for an aggression tribunal?

Yes. Outside Ukraine, support for establishing an aggression tribunal tends to be concentrated among Kyiv’s partners in the West. Ukrainian Foreign Minister Dmytro Kuleba has announced that over 30 states are working together to set up a special tribunal for the crime of aggression. Most appear to be Western. All the European Union (EU) member states have declared their full support for creating an “appropriate mechanism for the prosecution of the crime of aggression”, although as noted they have different views on what that mechanism should look like. After dragging its feet for some time, the U.S. in late March embraced the idea of an “internationalised” mechanism that appears to be a version of the hybrid option. Given longstanding U.S. concerns, particularly in the Pentagon, about exposing U.S. officials and personnel to international justice, it was likely difficult to arrive at this position.

By contrast, states in the so-called Global South have been much cooler to the idea of an aggression tribunal than Western counterparts. As Crisis Group has noted, many non-Western countries are happy to condemn Moscow’s aggression in general terms, but also eager to avoid backing more concrete penalties for Russia. With often fragile economies and their own national interests to look after, few of these countries want to be put in a position where they must choose between rival great powers squaring off in a war that is thousands of miles away. As discussed below, they are also conscious of the extent to which modern global criminal justice efforts have focused on countries like theirs, particularly those that have been adversaries of the West; by contrast, Western powers have largely skated away from being held accountable before international bodies for their own abuses (including in the wave of conflicts following the 11 September 2001 attacks). They may also be concerned about moves that appear escalatory and could make it more difficult to resolve a conflict that is already placing strains on a global economy struggling to recover from the COVID-19 pandemic.

Late in 2022, Ukraine unsuccessfully floated a UN General Assembly resolution endorsing the idea of a tribunal.

Some of these concerns have already emerged at the UN. In November 2022, only 94 of the UN’s 193 members backed a General Assembly resolution that floated the idea of Russian paying post-war reparations. Some, like Indonesia, argued that raising this option would only undercut future peace talks. Similar or stronger doubts would apply to the aggression tribunal idea. Late in 2022, Ukraine unsuccessfully floated a UN General Assembly resolution endorsing the idea of a tribunal and asking Secretary-General António Guterres to set out options for its creation. Guterres, already locked in difficult talks with Russia on preserving the Black Sea grain initiative, the deal struck in July 2022 allowing Ukraine to resume shipping grain by sea to the world market, indicated he wanted no part of the project, and the U.S., UK and many of Kyiv’s European allies have cautioned against bringing the plan to a vote. When the Assembly did vote on a broader resolution in support of Ukrainian sovereignty in February 2023, a mild paragraph about accountability drew comments from non-Western countries, which thought it could be counterproductive. Among those raising public concerns was Nigeria, a major African country that has otherwise been broadly supportive of Ukraine.

Some European diplomats who are keen to establish a tribunal say they think that a concerted Western lobbying campaign would change minds, but more sceptical officials predict the proposal might get as few as 60 and perhaps no more than 90 votes in the UN General Assembly.  

What are other concerns about establishing an aggression tribunal?

Many of the other qualms about establishing a new aggression tribunal overlap with concerns about an ICC investigation targeting the most senior Russian officials. Chief among them is that it risks sending a message that the West’s goal is regime change in Moscow. While in general proponents of an aggression tribunal do not explicitly advocate for that, the reality – which would not be lost on Moscow – is that Putin and his inner circle would both likely be targets and could only be meaningfully held accountable after losing power. Given the way that the crime of aggression is defined in the Rome Statute, it is widely accepted that the only potential defendants for an international aggression tribunal would be senior officials who are or were in a position to direct the Russian state’s military or political activities. Even a hybrid Ukrainian tribunal that lacks power to prosecute the troika now would likely be framed as a mechanism that could hold them accountable at an undefined point in the future when they no longer have power. 

As Crisis Group has argued, signalling an interest in regime change is both counterproductive and potentially dangerous. Such signals communicate to the Kremlin that its options are to win or to lose power and face prosecution, making the war existential for Russia’s leadership. Of course, the Kremlin may already perceive these to be the stakes, and in any event it shows no present signs of being interested in peace talks. Still, reinforcing the Russian leadership’s perceptions of this specific threat cannot help, as existential fears could increase their incentives to escalate, including potentially to nuclear use, if they foresee defeat on the battlefield. While Russia’s policy is not by any means to automatically use nuclear weapons if it is losing militarily, its published doctrine does allow for nuclear use if the state’s existence is at risk – and Putin and his team would not be the first world leaders to equate themselves and their government with the state.

There are further concerns besides.

First, Western powers could face even greater challenges dealing diplomatically with the Russian leadership on other priorities if they set in motion efforts to try them before an aggression tribunal. Thus far, despite bitter divisions over Ukraine, Western and Russian diplomats have continued working in the UN Security Council to manage other crises. Like the issuance of the ICC arrest warrants, establishing a tribunal to prosecute the crime of aggression could jeopardise such diplomacy and the benefits that flow from it – such as a renewed assistance mission to Afghanistan and a cross-border channel for humanitarian assistance to Syria.

Secondly, as noted above, prosecuting Russian leaders for the crime of aggression could complicate any future potential diplomacy on the conflict itself, however remote that prospect appears right now. If and when such negotiations get under way, Russia will almost certainly ask for discharge from criminal liability as part of any settlement. It is unclear how Western nations would meet this request if prosecution is proceeding in an international court (options one and two). As with an ICC prosecution, there may be theories by which the Security Council could use powers arising under the UN Charter that allow it to supersede most international obligations in support of such a settlement. But it is unclear whether Council members would agree to do so or whether such action would be widely seen as legitimate. If the tribunal is anchored in the Ukrainian judiciary (option three), then there may be more flexibility, in that Ukrainian officials may have options with respect to dropping charges or granting clemency. But both for political reasons, and because aggression is considered a crime of international concern for which impunity is impermissible, officials cannot be expected to publicly entertain this possibility at present.

Establishing an ad hoc tribunal to prosecute Russian officials alone would promote selective justice.

Thirdly, prominent international criminal lawyers, including a former ICC prosecutor, caution that establishing an ad hoc tribunal to prosecute Russian officials alone would promote selective justice, since it would have no jurisdiction over other crimes of aggression being committed around the world. These critics argue that the fairer approach would be to broaden the ICC’s aggression jurisdiction to eliminate its loophole for non-party states, so that both Russia and other non-members can be tried there. The selective justice critique – which hits home in many Global South countries – will be particularly stinging if the U.S. is closely associated with the establishment of a new tribunal. Russia could point out that the U.S. has hardly been a principled actor when it comes to prosecuting the crime of aggression. It could note that in Kampala, the U.S. shaped the Rome Statute amendments to shield itself from future prosecution. Moscow could also point out Washington’s checquered history when it comes to the use of force, including its 2003 invasion of Iraq (viewed by many as itself a war of aggression) and its defence of Israel’s annexation of the Golan Heights (viewed by many as an unlawful conquest).

Fourthly, at least some of the purported benefits of establishing a new tribunal seem questionable. There is little if any known evidence to suggest that Putin’s inner circle will be motivated to “peel off” by the prospect of prosecution for aggression. Nor, notwithstanding what some in Kyiv appear to believe, are criminal prosecutions for aggression either necessary or sufficient to cause Western powers to used seized Russian assets to compensate Ukraine. Finally, in terms of reinforcing the prohibition of the use of force and deterring future wars of aggression, it is not clear how establishing either an international or a hybrid court that is unable to bring Russian leaders to justice because they are not in its custody would advance those objectives. Indeed, there is a risk that if the process produces few or no successful prosecutions, it could perversely amplify the sense that aggression can be committed with judicial impunity.  

Proponents are aware of these concerns but tend to see the benefits of putting at least notional teeth into the prohibition of aggression – perhaps the most tangible opportunity since the Nuremberg trials – as outweighing them. As for the particulars, some might argue that because the notion of a negotiated peace with Putin seems far-fetched at present, any problems that a new tribunal might create for such a process are largely theoretical. Some would also dismiss the idea that Putin’s mindset will be significantly altered by the creation of a mechanism that will lack meaningful enforcement power, particular since the ICC has already targeted Putin with its recent arrest warrants. Finally, whether they say so or not, some of the governments backing the third (hybrid) option may also believe that a process rooted in Ukrainian law may ultimately be less threatening to the Kremlin and more flexible than a fully international process – including because it will give Ukrainian leaders options to drop charges, offer clemency and even engage in prisoner swaps.

What about trials in absentia?

Ukraine has suggested that a new tribunal could try the Russian leadership in absentia, though this idea has thus far garnered little support because of concerns about legitimacy. There is at least one precedent for in absentia trials of the crime of aggression. The International Military Tribunal at Nuremberg tried Adolf Hitler’s private secretary, Martin Bormann, in absentia – acquitting him of crimes against the peace but convicting him of war crimes and crimes against humanity and sentencing him to death. (It was later discovered that Bormann was already dead.) Despite this precedent, such trials have generally been disfavoured by subsequent international criminal tribunals. Ukraine has not publicly elaborated on the envisioned mechanics of in absentia trials and whether subsequent in-person proceedings would be conducted if the accused eventually came into custody. 

Would an aggression tribunal need to be established immediately?

At this stage, efforts to set up a new tribunal seem to have momentum. While Kyiv clearly does not favour the hybrid option for creating a new tribunal that has support from the U.S., France and Germany, it may not wish to buck such powerful patrons. Still, there is another option.

A new tribunal need not be established immediately. It need not be created in the midst of the fighting, while the outcome of the conflict, prospects for peace negotiations and the future compositions of governments in both Russia and Ukraine are still very much uncertain. In the unlikely event that forces inside Russia remove President Putin from power and make him available to stand trial abroad, a tribunal could be established at that juncture. In the meantime, states backing Ukraine could support efforts to investigate, gather and preserve evidence that might one day be presented in aggression trials should any be held. EU member states have agreed to support the establishment of an International Centre for the Prosecution of the Crime of Aggression in The Hague as a first step – a measure that the U.S. has also endorsed.

A staggered approach would have some apparent benefits. The standing up of a provisional body like the International Centre now, with action on a tribunal to follow when there is a prospect of actual prosecution, is less likely to complicate negotiations or so starkly imply that the West seeks regime change as establishing an international or hybrid tribunal for the explicit purpose of trying President Putin. Further, if the ultimate decision is for Ukraine to establish a hybrid tribunal based in Ukrainian law, it may face fewer hurdles under Ukraine’s constitution in the future when Ukraine is subject to neither martial law nor a state of emergency. Waiting would also address the risk of an international or hybrid tribunal electing to try Russian officials in absentia, which could be seen as undercutting fair trial safeguards and fairness values that the West is trying to promote.  

Waiting, of course, also has other implications, including the possibility that over time, politicians now focused on accountability will shift their attention to other things. Proponents of a new tribunal – who understandably do not wish to see an outrageous act of aggression go unpunished – will therefore almost certainly be reluctant to lose this moment of political will, at least among Western countries, to reinforce a norm that sits at the bedrock of international law. But while these views require careful consideration, so do the concerns noted above. The prospect that a misstep with respect to prosecuting the crime of aggression could exacerbate West-South divisions, impede peace negotiations or (even if only incrementally) fuel escalatory dynamics should not be waved away in the service of hoped-for normative gains of unproven value. Frustrating as it may be, the best course for the present may be to move deliberately – confining concrete efforts to the collection of evidence for an eventual prosecution if and when circumstances permit, while holding back on bolder steps until the day when both peace and justice can be more confidently served.

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