Ever since Russia launched its full-scale invasion of Ukraine in February 2022, some of the leading lights in international law have joined Ukrainian and Western officials in calling for the creation of a special tribunal to prosecute the Russian leaders responsible for initiating the brutal, illegal war. The tribunal would be set up specifically to try the crime of aggression—that is, a manifest violation of the UN Charter’s prohibition on the use of force. The International Criminal Court already has jurisdiction over Russian atrocities committed on Ukrainian territory. But aggression is a different kind of crime: it is about the decision to go to war in the first place rather than unlawful killings or other crimes committed during conflict. Because of a U.S.-backed loophole in the Rome Statute, the treaty that established the ICC, the court cannot bring aggression prosecutions against nationals of Russia, China, the United States, and all other countries that are not parties to the treaty.
Proponents have pressed to create a new judicial body to fill this gap, although most proposals only apply to the war in Ukraine. Former British Prime Minister Gordon Brown has argued that such a court is needed to fortify the norm against conquest, deter future aggressors, and afford a measure of justice for the war’s victims. “The crime of aggression is Putin’s original and foundational crime, the one that has been the starting point for all the other atrocities”, Brown wrote in February. Although supporters of this idea disagree about the form the new body should take, they agree that Russia’s aggression must not go unpunished in a court of law. Making the case for urgent and dramatic action to hold Russian actors responsible for aggression, international lawyers and advocates have described this as a new “Nuremberg moment”. In a May 4 speech in The Hague, Ukrainian President Volodymyr Zelensky himself invoked Nuremberg when he called for the establishment of a new aggression tribunal.
References such as this to the Nuremberg military tribunals, which took place after World War II to hold Nazi officials accountable for both aggression and atrocity crimes, are highly resonant but also misleading. The Nuremberg trials, as well as their counterparts in the Far East, came at the end of a globe-spanning total war that finished with the Axis powers’ defeat, surrender, and occupation, as well as the capture of their leaders. The Allies used these trials to demonstrate their commitment to the rule of law and to expose the defendants’ depravity. Because the Allies were able to impose terms on Germany or Japan, they were also in a position to try their leaders and enforce the sentences the war court passed down.
Russia’s unlawful war on Ukraine appears to be on a different trajectory. It is unclear how the conflict will end, but Russian surrender is not in the cards. One likely scenario is a negotiated deal; another is a frozen conflict. Moscow’s political leadership will remain almost certainly ensconced for the foreseeable future, and international actors will continue to need to work with them in forums such as the United Nations. Ukraine’s Western partners are trying to weaken Russia, but they are also trying to steer clear of a direct conflict, aware that any confrontation the Kremlin sees as posing an existential threat could bring the risk of escalation, including the use of nuclear weapons.
Plans to stand up a new tribunal do not easily fit into this landscape. Seeking accountability for Russian President Vladimir Putin and other senior Kremlin officials now, while Russia and Ukraine remain locked in combat, is hard to reconcile with any realistic Western war aims. A big push to prosecute Russian leaders for starting the war signals a desire to remove Russia’s leadership, risks escalation, and would almost surely complicate diplomacy to bring the war to an end. If establishing such a court ultimately proves futile, it could also weaken rather than strengthen the international criminal justice project. Rather than barreling ahead and risking a full-on collision between the interests of peace and justice, Ukraine and its partners should pursue a sequenced approach in which accountability efforts are better harmonized with the goals of conflict resolution.
A LOOPHOLE IN THE LAW
There are very few examples of war-time leaders being tried on aggression charges and fewer still of trials that took place while the leaders were still waging war. Most precedents date back to the post–World War II International Military Tribunal, which the victorious Allies created at Nuremberg to prosecute senior German leaders. The other most notable case comes from Nuremberg’s sister tribunal held in Tokyo, which was created to try Japanese officials. There have also been a handful of domestic trials, including those conducted in Ukraine following Russia’s 2014 occupation of Crimea, including one that resulted in the in absentia conviction of Ukraine’s former president, Victor Yanukovych.
This sparse record is no accident. The powers driving the creation of the post–Cold War architecture for international criminal law—the United States chief among them—were ambivalent about lumping together the crime of aggression with so-called atrocity offenses (genocide, crimes against humanity, and war crimes). U.S. officials worried about the lack of clarity and consensus regarding what constitutes aggression. They also feared the exposure they might be creating for themselves and up their chains of command. The U.S. government fretted that these legal changes would hamper Washington’s ability to build coalitions to undertake operations such as NATO’s intervention in Kosovo in 1999, which lacked UN Security Council authorization and which was widely seen as unlawful. (The United States has hewed to the position that its actions in Kosovo were “legitimate”, but it has not argued that they were legal.) Senior U.S. officials were also concerned about the ICC being drawn into political thickets that would undercut its effectiveness. They foresaw that the threat of being prosecuted for aggression could impel leaders to fight to the last rather than negotiate for peace.
Against this backdrop, the ICC Rome Statute did not cover the crime of aggression when it became effective in 2002. Instead, it bracketed the issue for a later date. When member states eventually did fill in the definitional gap at a conference in Kampala in 2010, the United States quietly insisted on including a loophole that prevented the court from exercising jurisdiction over a charge of aggression against nationals of countries that were not parties to the Rome Statute, a group that includes China, Russia, the United States, and several other significant military powers, such as India, Israel, and Turkey. Moreover, even with this level of protection secured for itself, Washington did not warm to the idea of aggression as an international crime. After the Kampala conference, U.S. officials lobbied ICC member states not to ratify the aggression amendment, hoping to forestall the moment when it would come into effect, and to narrow the scope of its applicability.
Ultimately, despite U.S. efforts, the amendment took effect in 2017. But with the ICC already struggling with its caseload, and given political headwinds from the United States and elsewhere, at least some experts expected that the crime of aggression would move to the back of the international legal agenda for the foreseeable future.
RUSSIA BREAKS THE RULES AND CHANGES THE GAME
Russia’s invasion of Ukraine in February 2022 rocked the international law community. Appalled by Russia’s vast criminality—and seeing both an opportunity and an imperative to reinforce the global norm against illegal war—prominent Western scholars joined former officials (and some current ones) in calling for the creation of a judicial body that could close the international legal gap and punish Russia for its trespasses. These efforts were spurred on by vigorous Ukrainian advocacy.
Arguments in support of an aggression tribunal ranged from the moral to the practical. Many have argued that prosecuting Russian officials would be necessary to deter future wars of aggression. Brown has invoked the Nuremberg tribunal’s observation that aggression “is the supreme international crime” in that it is the parent of all criminality that happens in war. Law professor Oona Hathaway has noted that pursuing Putin and his associates for war crimes and other atrocities (as the ICC is already doing) would fail to account for lives and property lost in actions that may technically be permissible under the laws of war. International lawyer Philippe Sands has argued that prosecuting Putin before an international tribunal would further delegitimize him, possibly create an incentive for those in his inner circle to “peel off”, and perhaps offer Ukraine leverage in future negotiations.
To date, expert discussion and media coverage have tended to focus mainly on different models for overcoming the technical barriers to prosecution while glossing over the impracticality of these proposals. The technical issues are significant: although Ukraine’s domestic courts already have the authority to try Russians for aggression, they would almost certainly be required under international law to recognize immunities for Russia’s heads of state and government, as well as its foreign minister. Thus, a Ukrainian prosecution of Putin, at least while he is in office, would not be possible. And it’s unlikely that any prosecution on charges of aggression against Ukraine that excluded the key architect of the war would be seen as legitimate, especially since the Rome Statute definition of aggression applies only to those in a position to control or direct a state’s armed forces.
Against this backdrop, Ukraine (together with some of its Eastern European partners and many experts) has pressed for the creation of an international tribunal by means of a UN General Assembly resolution. A tribunal backed by the General Assembly might stand a greater, although not certain, legal chance of being able to prosecute Russia’ top leaders. Unless they came into the tribunal's custody, however, it would have to do so in absentia.
By contrast, many of Ukraine’s most important Western partners, initially led by Germany, have instead endorsed the creation of a “hybrid” court within the Ukrainian system that would draw on “international elements”. What this would entail remains vague: it might mean Ukraine’s Western backers lending advisers or financial support to Ukraine; establishing the court outside Ukraine, possibly in the Hague; or even the application of non-Ukrainian law in any prosecution by the tribunal. Germany has conceded that a hybrid tribunal would be unable to prosecute Putin while he remains in office, although such a court might at least prosecute some military leaders and Duma members who voted for the war.
Given decades-old U.S. reservations about prosecuting the crime of aggression, it was unclear whether Washington would support any of these models. But in March, after extended deliberations within the Biden administration, the U.S. government announced that it was lining up behind an “internationalized national court” along the lines of the German approach. Weeks later, the G-7 endorsed this approach. Even though this represented a remarkable movement away from the traditional U.S. posture, the reaction from Kyiv was distinctly chilly. Andrii Smyrnov, the deputy head of Ukraine’s Presidential Office, suggested that a hybrid tribunal would be unconstitutional and expressed concern that it would demote the crime of aggression to a bilateral dispute rather than a matter of international concern. Other Ukrainian officials and frustrated scholars worried that an aggression court with no hope of prosecuting Russia’s top leader would not be worth its salt, and they criticized the United States for showing too little ambition at a historic moment. At his speech in The Hague, Zelensky flatly rejected the hybrid model, calling into question the viability of an approach that presupposes Ukrainian buy-in and cooperation.
REAL WORLD WORRIES
The technical challenges surrounding efforts to set up an aggression tribunal are significant, no matter which model is pursued. But the even bigger—and in our view more consequential—geopolitical costs and practical challenges of creating such a tribunal tend to be overlooked. A fuller reckoning would recognize that to establish an aggression tribunal at this moment in the war would be difficult to reconcile with both global attitudes and battlefield realities.
First, states in the so-called global South have been decidedly cool to the idea of aggression prosecutions. With often fragile economies and their own national interests to look after, few want to be put in a position where they must choose between rival great powers squaring off in a war that is for them geographically remote. These countries are also conscious of the extent to which modern global criminal justice efforts have focused on countries such as theirs, particularly those that have been adversaries of the West. By contrast, they consider that Western powers and their partners have been ringfenced from facing accountability for their own abuses in places such as Afghanistan and Iraq.
These concerns have started to surface at the UN. 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. Some skeptical European officials have predicted that such a proposal to establish a tribunal might get as few as 60 and perhaps no more than 90 votes—out of 193 member states—if a vote is held in the UN General Assembly. At a recent Brookings Institution event, Martin Kimani, Kenya’s ambassador to the UN who forcefully denounced irredentism and the unlawful use of force on the eve of Russia’s invasion, cautioned against “believing that legalism will deliver us from this major conflict and its escalation dangers”. For Western states eager to maintain the most united possible global front against Moscow, these words—from perhaps the United States’ closest partner in East Africa—merit careful consideration.
A second basket of concerns is more practical. Simply put, proceedings that target Russia’s sitting leadership clash with Western objectives in a way that the post–World War II prosecutions of German leaders did not. Probably most worrying is what these efforts communicate to Moscow about the West’s designs for effecting regime change in Moscow, an end state that Western leaders have taken pains to say they do not seek. Creating a tribunal would signal to the Kremlin that its options are either to win and remain free or to lose and face prosecution, making the war’s stakes existential for leaders that control the world’s largest nuclear arsenal. (Arguably arrest warrants that the ICC has issued against Putin and one of his commissioners already do this; creating an aggression tribunal would unhelpfully reinforce that message.)
Creating a judicial body to prosecute Russian leaders for the crime of aggression would also complicate future diplomacy. If and when negotiations to end the war get underway, Russia will almost certainly ask for a release from criminal liability as part of any settlement. It is unclear how Western countries would respond to this request. The UN Security Council may have powers that would allow it to supersede international obligations relating to the tribunal, and Kyiv might be able drop charges or grant clemency in the case of a hybrid court, but political considerations could make it hard to wield these tools. Standing up a new aggression court could also gum up what little is left of East-West diplomacy on issues such as the Black Sea grain deal, as well as priority areas distinct from the war, including humanitarian access in Syria, assistance in Afghanistan, and peacekeeping in Africa.
The last area of concern is in the realm of principle. An ad hoc tribunal created to prosecute Russian officials would have no jurisdiction over crimes of aggression being committed outside Ukraine—giving a free pass to Western countries and their partners. This would only reinforce the view of global South countries that the United States and its allies see international criminal justice institutions as a selective tool that applies only to their adversaries.
MOSCOW IS UNLIKELY TO FALL
Perhaps these would be risks worth taking if the purported benefits of establishing a new aggression court were certain, but many of the asserted upsides seem more rooted in aspiration than a sober assessment of costs and benefits. The reality is that a nuclear-armed Russia is not analogous to Nazi Germany after its defeat, nor to the countries and regions where ad hoc tribunals had some success in the post–Cold War period. Putin and his inner circle are well entrenched. Few analysts see much likelihood of them leaving power either during or at the end of the war. It is no easier to imagine Russia surrendering Putin (or for that matter Duma delegates or Russian flag officers) than it is to imagine the United States surrendering Bush administration officials to a judicial body for invading Iraq.
Thus, whatever form an aggression court or tribunal takes, it will have to make a choice. It can conduct trials in absentia, which would hardly make the court a beacon of due process and the rule of law. Or it can pursue no trials at all, and risk perversely amplifying the sense that aggressors can act with impunity. In the meantime, there seems little reason to hope that the unenforceable threat of prosecution for aggression will create useful leverage over the Kremlin or lead to the “peeling away” of his inner circle.
So why do proposals for an aggression tribunal continue to enjoy the traction that they do? The prospect of entrenching the norm against aggressive war has enormous appeal. As international lawyers, we are familiar with the stirring speech that U.S. Supreme Court Justice Robert Jackson, on loan to the Nuremberg tribunal, offered in his opening remarks on November 21, 1945, when he spoke of the proceedings as “one of the most significant tributes Power has ever paid to Reason”. We also share the fervent wish to see power once again bend the knee to international law in the service of a more peaceful world. Right now, however, that lies outside the realm of the possible, and trying to create legal accountability without adequate consideration of the impact on conflict resolution in Ukraine could well render a horrific situation that much messier.
But there are other options. Rather than pushing forward to establish a new judicial body at this time, the United States and Ukraine’s other partners should lay out a more cautious, phased approach. They should convey to Kyiv, as well as the experts who are pushing for more robust measures, that it would be unhelpful to take further steps toward setting up a new court or tribunal in the midst of the fighting. At the same time, they should reinforce their support for the International Centre for the Prosecution of the Crime of Aggression in The Hague as a first step to assisting in any eventual prosecutions. This interim prosecutor’s office is tasked with supporting and enhancing investigations into the crime of aggression. The United States has endorsed this body and U.S. Attorney General Merrick Garland recently announced that an experienced U.S. federal prosecutor would be detailed to this body. These are meaningful moves, but they are less likely to be seen as directly threatening Kremlin leadership, or to complicate any peace talks, than the creation of a new court or tribunal designed specifically for Ukraine.
If history takes an unexpected turn and Russian leaders wind up available to stand trial abroad, then it will be time to talk about a new judicial body. In the meantime, Ukraine’s Western partners should continue helping Ukraine frustrate Russia’s aggressive designs on the battlefield and gathering evidence of its crimes. They should hold back on bolder steps until the day when the ends of peace and justice are more clearly aligned, and Nuremberg’s legacy can be more fully honored.
Brian Finucane is Chief of Policy at the International Crisis Group. During the Obama administration, he served as Special Assistant to the President and Senior Director for Multilateral Affairs and Human Rights at the National Security Counciland as Assistant Legal Adviser for Political-Military Affairs at the U.S. State Department. Stephen Pomper is Senior Adviser in the U.S. Program at the International Crisis Group and a Nonresident Senior Fellow at the Reiss Center on Law and Security at New York University School of Law. During the Obama and Trump administrations, he served as an Attorney Adviser in the Office of the Legal Adviser at the U.S. State Department.