In the past year, discussions about a Special Tribunal for the Crime of Aggression (STA) against Ukraine have shifted from whether to establish such an institution to the related question of how best to do so. Two main options have emerged: (1) a (purely) “international” tribunal created through a bilateral treaty between Ukraine and the United Nations on the recommendation of the U.N. General Assembly, and (2) some form of “hybrid” or “internationalized” tribunal, which would combine international and domestic legal elements. On Sept. 22, the Core Group of Friends for Accountability, which currently comprises 38 States advocating for aggression trials, is scheduled to meet in The Hague, Netherlands, to continue diplomatic negotiations. The tribunal’s institutional design will feature prominently on the main agenda.

While much ink has been spilled on the crime of aggression since Russia’s full-scale invasion of Ukraine in 2022, the most pressing question now is which of the competing models is better suited to address aggression. Diplomats should pay close attention to how this question is answered. Although choices of institutional design may seem like technical disputes among lawyers, the question of how to prosecute aggression may have consequences as far-reaching as whether to seek punishment for Russia’s behavior at all. Indeed, the increasingly polarized debate over the tribunal’s institutional design – international or hybrid – goes to the heart, and core purpose, of international criminal justice, especially its ability to serve as a counter-hegemonic force aiding the victims of abuse by powerful States.

While various arguments have been advanced for and against both models over the past year, an international tribunal appears to offer greater promise – subject to a caveat relating to in absentia trials – for the development of international criminal law. By contrast, opting for a hybrid approach may have conservative effects and facilitate great power impunity. Given the high stakes of these conversations, supporters of accountability, especially from smaller and weaker States, would be well advised to make their views known in the coming weeks and months.

How Did These Two Options Emerge?

In recent months, the debate over what kind of tribunal should prosecute Russia’s aggression has become more prominent. Although Ukraine and its allies, especially States from Eastern Europe, embraced an international tribunal in the months after Russia’s full-scale invasion, the main Western powers hedged their views and ultimately came out – beginning with Germany, followed by the U.K. and the United States – in favor of a hybrid tribunal based on Ukraine’s domestic jurisdiction. Diplomats from Ukraine initially appeared non-committal, but the special tribunal’s institutional design became more pressing as negotiations shifted from whether to how the tribunal should proceed.

In May 2023, Ukrainian President Volodymyr Zelenskyy forcefully rejected the idea of a hybrid tribunal, emphasizing that approach would replicate the flaws of previous Western-imposed arrangements like the 2014-15 Minsk accords, which produced only a “hybrid peace.” However, Ukraine’s clear preference for an international tribunal has faced resistance, with recent statements by Ukrainian diplomats (see here, here and here) pointing to an entrenched split between Western powers in the G7 and a host of other States forming the Core Group (31 others in total, including a cross-regional panoply of members from Western States, Eastern Europe and Latin America). With Ukraine’s Presidential Office hinting that diplomatic negotiations cannot drag on forever and should ideally be finalized by the end of 2023, there is now talk of a compromise solution consisting of a third State’s – as opposed to Ukraine’s – jurisdiction serving as a base to ground the Special Tribunal’s powers. While this new “third State” model avoids some problems of a hybrid tribunal based on Ukraine’s jurisdiction, it replicates other hybrid design features favored by Western powers, especially the applicability of immunities for Russia’s top leadership. This in turn explains why the Ukrainian government continues to advocate for an international tribunal.

Given the public disagreement between Western powers and other “Friends of Accountability,” it is worth examining the main arguments for and against each model, before assessing the global stakes of this conversation.

The Arguments For an International Tribunal

There are several arguments for an international tribunal. The chart below distills them. Unlike a hybrid tribunal based on a country’s domestic jurisdiction (that of Ukrainian or a third State), an international tribunal created using a treaty between U.N. and Ukraine – like the Special Court for Sierra Leone – could argue persuasively that it does not have to recognize the personal immunities of the Russian troika (the current head of State, prime minister, and foreign minister). Put differently, an international tribunal could issue arrest warrants for the presumed masterminds behind Russia’s aggression and – provided it obtains custody – put them on trial for the crime of aggression.

In addition to the issue of immunities, an international tribunal recommended by the General Assembly would enjoy greater legitimacy than a purely national court that is exercising its own domestic jurisdiction over aggression. Given the long history of imperial and colonial exploitation that underpins this war, international prosecutors and judges would be seen as more impartial than their Ukrainian counterparts who would be asked to sit as judge and jury in a case over the invasion of their own country. Equally important, an international tribunal set up by a significant number of States would create a precedent, deterring great power intervention in the future and, if such cases do occur, facilitating a coordinated response. It is no coincidence that diplomatic negotiations on the special tribunal have spurred a parallel effort to amend the Rome Statute’s flawed Kampala jurisdictional regime that prevents the International Criminal Court (ICC) from addressing aggression on Ukrainian territory – unlike the war crimes, crimes against humanity, and acts of genocide that are already being investigated by ICC Prosecutor Karim Khan.

Although there is some disagreement among experts as to whether the General Assembly has the legal power to disregard the troika’s immunities under customary international law, the main sticking point is not legal, but political: how many States would have to vote in favor of such a tribunal to give it sufficient legitimacy and set aside immunities for what the General Assembly has previously condemned as “aggression by the Russian Federation against Ukraine in violation of Article 2(4) of the [United Nations] Charter.” Some commentators set the legitimacy threshold as high as a two-thirds majority of voting States, but the better view is that Ukraine should leverage its anti-imperial and post-colonial credentials to build a cross-regional coalition and that a simple majority of voting States would suffice (the threshold also depends on whether Ukraine opts for a General Assembly resolution under the “Uniting for Peace” framework or by ordinary procedure). However, with only 38 States from South America, North America and Europe making up the Core Group’s membership – and Asia and Africa unrepresented up to this point – some have pursued an alternative institutional model for the Special Tribunal.

The Arguments for a Hybrid Tribunal

Proposals for some type of mixed, non-U.N. sponsored institutional design date back to mid-2022, but the current proposal appears to be a special tribunal based on the jurisdiction of a third State, with the Netherlands as a likely candidate. Although the legal details are still unknown, the working assumption is that such a hybrid (the label “internationalized” has been used more frequently of late, but nothing hinges on this semantic distinction) Special Tribunal would be acting on the basis of Ukraine’s delegated jurisdiction or, more controversially, pursuant to a third States’ universal jurisdiction to prosecute the crime of aggression (only a few States recognize universal jurisdiction over this crime, including Poland and the Baltic States). The third State institutional setup, which appears untested at other international criminal tribunals, avoids various complications that have hampered discussions of a hybrid tribunal based on Ukrainian law, including a constitutional prohibition on creating such an institution during wartime.

However, while the existence (or not) of Ukrainian, Dutch or other countries’ jurisdiction over the crime of aggression is a pre-requisite for any diplomatic negotiation of a Special Tribunal, the question remains what benefits this model offers compared to the international model. In other words, why should diplomatic delegations support a hybrid tribunal for aggression, which – according to recent reports – will be put to a General Assembly vote anyway? In this regard, advocates of hybridity have been more circumspect, with arguments falling under a “positive” and “negative” rubric.

Among the positive arguments, U.S. Ambassador At Large for Global Criminal Justice Beth Van Schaack has emphasized that a hybrid tribunal will build the capacity of Ukraine’s justice system. As I have explained elsewhere, these arguments – based on examples from Africa and Asia, where hybrid tribunals were created to deal with hundreds of atrocity crimes, and against the backdrop of State fragility – are not persuasive when it comes to Russian aggression against Ukraine. Unlike investigations into thousands of war crimes and crimes against humanity, aggression trials in the Ukraine context will happen only a handful of times, and without any downstream effect on Ukrainian judges’ expertise on this specific crime. Moreover, not only will Ukrainian magistrates not be perceived as credible judges in their own case, plans for a hybrid tribunal – whether based on Ukraine’s or another State’s jurisdiction – take for granted that such an institution would be physically located outside of Ukraine, which would in turn reduce its potential “spill-over” or “demonstration” effects on the domestic rule of law. In short, the so-called “positive” case for hybridity seems to copy-paste institutional models from different geographical contexts, whereas meaningful transitional justice is about tailoring approaches to a specific context and avoiding “one size fits all” formulas.

This leaves negative arguments that – as insiders acknowledge off the record – are the unstated albeit real reason for the current discussions about a hybrid model. Both the U.S. and German governments have emphasized concerns about insufficient support for a General Assembly resolution, which they link to allegations of “double standards” in international criminal law (discussed later). The bottom line is that, led by the United States and Germany, the G7 support a hybrid model less on grounds of principle rooted in the tribunal’s purported benefits, and more out of a fear that an international model might not receive sufficient votes to make it international. What explains this fear of the unknown?

Immunities and the Crime of Aggression

This brings us to the G7’s second negative argument: immunities. As observers widely acknowledge, in line with consistent jurisprudence, only an “international” tribunal may have the legal power to pierce the personal immunities of the Russian troika, otherwise enshrined in customary international law. By contrast, a “mere” hybrid tribunal would, in principle at least, lack the legal power to do so. Notwithstanding this fundamental difference of institutional design that appears to speak in favor of an international model, the United States has brushed these considerations aside, suggesting that a hybrid tribunal’s inability to overcome immunities does not matter because a trial will only happen if Russian President Vladimir Putin is deposed as head of State, in which case immunities would cease to apply. Put differently, because it is very unlikely the Russian leadership will be arrested and prosecuted while still in office, a hybrid tribunal is an equally acceptable model because their personal immunities will never matter in practice.

Although this consequentialist argument may seem plausible at first blush, it amounts to a bait and switch, which distracts from the fundamental legal principles that are in play as diplomatic negotiations continue. Contrary to what advocates of hybridity may claim, it matters greatly for international law whether a tribunal is created with the power to investigate, issue arrest warrants, prosecute, try and sentence the people it has jurisdiction over from the outset.

For starters, from a pragmatic, resource-oriented perspective, it is not clear why States would establish a tribunal that, by its own advocates’ admission, lacks the legal powers to do the main thing it is purportedly established to accomplish. If a factual pre-requisite for a tribunal to exercise its powers is missing, would it not make more sense to wait for the facts to change and then propose an institution to deal with the fallout? Counterarguments to the effect that the facts surrounding Russia’s aggression should be investigated are unpersuasive, because they again overlook that aggression trials will not be an extended series of multiple proceedings relating to thousands of atrocity crimes, but rather a time-limited inquiry into a single set of acts, the facts of which are already relatively well known. Moreover, given that an investigative body, the International Centre for the Prosecution of Aggression, is now up and running, advocates of hybridity must still answer the following question: what is the value added of their tribunal today?

In this regard, the U.S. argument about immunities overlooks a crucial point about how international law is made and how it can have a real impact on international relations. To be sure, Ukraine and a handful of States can create a paper (hybrid) tribunal today, wait for the facts to change, and then – if anyone still thinks this necessary – ask the General Assembly to provide the international community’s blessing for a fait accompli. Ukrainians will indeed secure a modicum of accountability if Putin is deposed and eventually put on trial for aggression before such a hybrid tribunal. But the legal consequences of that type of trial against a deposed head of State would be miniscule compared to what an international tribunal could accomplish, which brings us to the crux of the debate that must be resolved in the near future.

Unlike a hybrid tribunal, which by its sponsors own admission would lack the power to pierce Putin’s immunities, an international tribunal could issue an arrest warrant for Putin without waiting for regime change in Russia. So why does an arrest warrant matter even if the Russian leadership cannot be (immediately) arrested? In realpolitik terms, a warrant issued by an international tribunal, created with the General Assembly’s approval, further delegitimizes Putin and increases the likelihood of his eventual fall from power. It is well known that Putin did not attend last month’s BRICS summit in South Africa because of the legal complications caused by the ICC’s arrest warrant against him, with reports suggesting Brazil now faces the same dilemma. Equally important, the very fact of issuing an arrest warrant for Putin creates a momentous legal precedent by confirming that the troika enjoy no personal immunities for the crime of aggression before a tribunal with jurisdiction over such a crime (it should be remembered that a tribunal must have the legal authority to issue such warrants, lest States relive the controversy over former Sudanese President Omar al-Bashir’s immunity, where doubts about the ICC’s powers enabled non-cooperation from States for many years).

Not only would arrest warrants from a legally empowered institution constitute, in and of themselves, a progressive interpretation of the law on immunities; they would also have immense counter-hegemonic potential, aimed at the leadership of a U.N. Security Council permanent member State. In fact, the value of an arrest warrant for aggression would likely be greater than an in absentia trial of Russia’s leadership. While Ukraine appears to favor such a trial – where the accused would be prosecuted in their absence – in absentia proceedings are widely seen as contentious under international law, and should be avoided when possible.

It bears emphasizing that, conversely, a hybrid tribunal established now, while Putin remains in power, risks amounting to a conservative and regressive endorsement of the contrary international legal proposition. Indeed, it would imply that the troika’s personal immunities protect them from prosecution for a core crime like aggression, despite there being a (paper) tribunal for such prosecutions. And, contrary to suggestions by hybridity advocates, this negative precedent would be exacerbated by a hybrid tribunal issuing warrants for senior Russian officials other than the troika, for instance the minister of defense, as this could constitute customary law in favor of the troika’s immunities. If, as recent reports suggest, the General Assembly is expected to endorse the hybrid model, it appears the international community would be asked to validate a regressive legal precedent that enshrines the immunity of a permanent Security Council member’s leadership, despite the General Assembly’s prior condemnations of Russia’s unlawful behavior.

In short, far from irrelevant, the G7’s negative arguments in favor of a tribunal that corroborates Putin’s immunity are, in fact, a conservative ploy that sets the law back and makes it less likely that he will be deposed. Instead of sending a message about the inapplicability of immunities for the crime of aggression, advocates of hybridity would succeed in reinforcing an unequal legal landscape that benefits powerful hegemons like the United States or China, and even “middle powers” like Turkey or Iran, who could later leverage the Ukraine precedent to argue for their leadership’s immunity from prosecution.

The Misleading Debate over “Western” Double Standards

It should come as no surprise that the main Western powers accused of unlawful interventions in the last twenty years – the United States, the U.K. and France – have endorsed a tribunal that makes it less likely their leaders will be prosecuted before an analogous tribunal (or any tribunal) in the future. However, a remarkable aspect of the ongoing diplomatic negotiations is how Western government officials increasingly leverage critiques of “Western double standards” to accomplish this regressive development. The irony should not be lost. Drawing on misleading critiques that analyze global divisions over the Special Tribunal through a reductionist “Global South versus West or Global North” binary, the same Western powers that intervened with impunity in Iraq are now making accountability for Russia and future aggressors less likely out of a purported concern that their prior actions in the Global South have not been adjudicated. Incredibly enough, like the Trump administration’s faux embrace of critiques leveraged against the ICC to justify sanctioning its “rogue” former prosecutor, the G7 now claim to favor a hybrid court because a General Assembly-endorsed, Ukraine-specific Special Tribunal would risk antagonizing the same Global South nations. Put differently, hybridity is the answer because an international tribunal for Ukraine would supposedly exacerbate – rather than reduce – the impunity of great powers.

As explained at length here, the “Western double standards” narrative, including suggestions that Ukrainians would be “privileged” at the expense of Global South victims, discounts the counter-hegemonic potential of aggression trials in the “Global East” and their ground-breaking precedential value for smaller and weaker States in all regions. By making the perfect the enemy of good, these types of arguments play into the hands of Western powers and ultimately serve to mask the regressive and conservative consequences that flow from a paper (hybrid) tribunal or, equally bad, no special tribunal being established at all. In short, States who ignore Ukraine’s accountability demands out of an (understandable) frustration with the impunity of Western powers risk cutting their nose off to spite their face.

Squaring the Circle and the Way Forward

As diplomatic negotiations on a Special Tribunal for Aggression against Ukraine continue in the weeks and months ahead, the world faces a set of urgent questions with consequences far beyond the case of Ukraine. It is important to recognize that the success or failure of this tribunal will shape the parallel negotiations on amendments to the Rome Statute’s aggression regime, which advocates of an international tribunal have spearheaded for months.

It will also set a precedent with consequences for international law more broadly for two reasons. First, despite the claims of hybridity advocates, the choice of institutional design matters greatly for the evolving debate over immunities for international crimes. An arrest warrant for Putin would create a momentous precedent that a head of State of a Security Council permanent member and global hegemon does not enjoy immunity for aggression, which could in turn precipitate his fall from power. Second, even if the Rome Statute’s jurisdictional regime for aggression is eventually amended, the ICC’s incomplete membership by States means that the Ukraine precedent will likely constitute a litmus test for the foreseeable future as to whether and how powerful States can be held accountable for future cases of aggression. In this regard, States must ask themselves what model has a greater deterrent effect, making it less likely that a future aggressor will use force in violation of the U.N. Charter.

Understandably, many States are wary of antagonizing a nuclear power like Russia. However, the uncomfortable truth is that if either a weak institutional model is chosen or no tribunal is established at all, today’s decisions, or lack thereof, will have downstream effects for future victims of great power intervention. As the Chilean President, Gabriel Boric, remarked at an EU-Latin America summit in July 2023, “today it is Ukraine, but tomorrow it could be any of us.” People in weaker and smaller States around the world should pay close attention to this conversation, as their future may depend on its outcome.

IMAGE: Ukrainian President Volodymyr Zelenskyy and Secretary-General of the United Nations Antonio Guterres shake hands during the joint press conference following their meeting on March 8, 2023 in Kyiv, Ukraine. (Photo by Roman Pilipey/Getty Images)