(Ця стаття також доступна українською мовою тут.)

Russia’s aggressive war against Ukraine is one of the clearest violations of article 2(4) of the United Nations Charter since its entry into force. In addition to legal implications for the  responsibility of Russia as a state, the events have generated renewed interest in the possibility of individual accountability for the crime of aggression. Although not punished at the international level since World War II,  planning, preparing, initiating, or waging (sometimes termed “executing”) such a war has been recognized as criminal under customary international law since findings to that effect by the International Military Tribunals at Nuremberg and Tokyo in the 1940s, as exemplified by the consensus affirmation of the UN General Assembly in 1946 and 1974 and the 2017 agreement of the 123 States Parties to the International Criminal Court (ICC). The question, of course, is whether and how criminal cases could be prosecuted in this instance.

Multiple efforts are already underway. Poland has reportedly initiated an aggression investigation relating to the invasion of Ukraine, pursuant to art. 117 of its criminal code. A group of eminent lawyers and public figures has issued a statement calling on countries to “agree to grant jurisdiction arising under national criminal codes and general international law to a dedicated criminal tribunal, and [to] confer on such a tribunal jurisdiction to investigate both the perpetrators of the crime of aggression [against Ukraine] and those who have materially contributed to or shaped the commission of that crime.” In very short order, this initiative was launched and discussed by a high-profile panel at Chatham House, at which Ukrainian Foreign Minister Dmytro Kuleba urged the tribunal’s creation, noting explicitly that he was doing so in his official capacity (at 18:12). In the course of that discussion, Phillippe Sands stated that a number of “very significant countries” were taking the idea “very seriously” (at 43:56). Complementing this initiative, it has also been suggested that the UN General Assembly could cooperate with Ukraine in the creation of a hybrid tribunal. Efforts along these lines have been endorsed by The Elders.

The burgeoning political will to pursue criminal accountability for this particular war of aggression is striking both for the publicity surrounding it and for its historical rarity. Questions relating to jurisdiction, immunities, and the wisdom of such initiatives abound. In addressing those questions below, one analytic point, among others, becomes clear. The creation of a tribunal with the support of a UN General Assembly resolution would place it on the firmest footing. Before considering each of those issues, however, it is necessary first to clarify the scope of criminal responsibility for aggression.

A Leadership Crime

Unusually among international crimes, individual liability for waging aggressive war attaches only to those in leadership positions. This, however, does not mean that liability is restricted to the single individual at the apex of a state’s command structure. As articulated in the High Command case at Nuremberg, the leadership element limits criminal responsibility to those “in a position to shape or influence the policy that brings about [the criminal war’s] initiation or its continuance after initiation, either by furthering, or by hindering or preventing it.” (p.488) The ICC’s jurisdiction is limited to those in a position “effectively to exercise control over or direct the political or military action of a state.” (art. 8 bis(1)). It has been suggested that the latter standard is narrower than that elaborated at Nuremberg, although its precise scope has yet to be tested and one might question whether any narrowing reflects customary international law. It is notable in this respect that those advocating the creation of a special tribunal for the current war have invoked language reminiscent of Nuremberg, calling for the tribunal to hold accountable those “who have materially contributed to or shaped the commission” of aggression.

Vladimir Putin exercises significant control within the Russian Federation. So too does Alexander Lukashenko in Belarus, which is implicated here on the grounds that “allowing” one’s own territory to “be used by” another state “for perpetrating an act of aggression against a third State” can itself qualify as a criminal act of aggression without needing to resort to secondary modes of liability. (art. 8 bis(2)(f)). However, the Nazi regime in Germany was also highly centralized. And yet, the International Military Tribunal (IMT) reasoned,

Hitler could not make aggressive war by himself. He had to have the cooperation of statesmen, military leaders, diplomats, and business men. When they, with knowledge of his aims, gave him their co-operation, they made themselves parties to the plan he had initiated. They are not to be deemed innocent because Hitler made use of them, if they knew what they were doing. That they were assigned to their tasks by a dictator does not absolve them from responsibility for their acts. (pp.468-469)

The Tribunal went on to convict twelve senior Nazi officials of planning, initiating, or waging wars of aggression. Three additional Nazi officials were convicted in the subsequent Ministries case. Having committed suicide prior to capture, Hitler himself was never in the dock. On a similar basis, the International Military Tribunal for the Far East convicted twenty-four Japanese officials of planning, initiating, or waging wars of aggression or conspiring to do so. Emperor Hirohito was famously omitted from the trial’s ambit for political reasons.

It is difficult to know at this stage how many individuals might satisfy the leadership element as it pertains to the invasion of Ukraine. However, the broadcast of Russia’s Security Council meeting in advance of the war revealed a range of senior officials participating in what could be characterized as part of the planning or preparation for aggressive war. In addition, it is at least conceivable that those leading the Wagner group could qualify, having reportedly sent their mercenaries into Ukraine on Russia’s behalf—a specifically identified act of aggression within the ICC definition (art. 8 bis(2)(g)).

Whether controlling an aggressive act within an aggressive war is sufficient for criminal liability remains to be seen. Two precedents from Nuremberg are worth noting in that respect. First, the IMT convicted Karl Dönitz of waging aggressive war despite finding that he was not privy to the conspiracy to wage such war and despite the fact that he did not control the overall military campaign prior to 1943. His crime in the early years inhered in his control of the aggressive use of submarine warfare (p.556). Second, the tribunal in the I.G. Farben case recognized that criminal liability for aggression could attach to “persons in the political, military, and industrial fields … who were responsible for the formulation and execution of policies.” (p.1124, emphasis mine). If any in the private sector can be criminally liable for aggression, those who send mercenary groups to kill on behalf of an aggressor state would surely be top of the list.

Ultimately, in considering the leadership element, the important point at this stage is that efforts toward criminal accountability for this war are not simply about prosecuting Putin. More controversially, it is also worth noting that liability for the crime of aggression as understood in Ukrainian criminal law is not limited to leaders in the first place (p.1096).


There are four possible jurisdictional paths worth considering for the prosecution of aggression crimes in Ukraine: the International Criminal Court, an ad hoc international tribunal (whether along the lines proposed at Chatham House or pursuant to a General Assembly resolution), a domestic court exercising territorial jurisdiction (in Russia, Belarus, or Ukraine), or a domestic court exercising universal jursidiction.

Despite the fact that neither Ukraine nor the Russian Federation is party to the ICC Statute, Ukraine’s ad hoc acceptance of the Court’s jurisdiction under article 12(3) of the Rome Statute provides the Court with jurisdiction over crimes against humanity, war crimes, or genocide arising in the current conflict. The Prosecutor has already opened an investigation covering such crimes. However, this investigation will not include aggression. The ICC Statute specifies that “the Court shall not exercise its jurisdiction over the crime of aggression when committed by [the] nationals or on [the] territory” of a state not party to the Statute (15 bis(5)). Even if both states were to become ICC States Parties, their ratifications would not have retroactive effect (art. 11(2)). An article 12(3) declaration can have retroactive effect, but it does not render the declaring state a state party. As such, it is unlikely that such a declaration can overcome the obstacle posed by article 15 bis(5). Moreover, the terms of article 15 bis(5) combined with an understanding embedded in the resolution activating the Court’s jurisdiction over aggression (para. 2) would suggest that any path to criminal jurisdiction via article 12(3) would need to come through the ad hoc acceptance of the aggression amendments by both the aggressor state and the attacked state. It is currently inconceivable that Russia or Belarus would grant such consent. Similarly, although jurisdiction over aggression would be straightforward if the UN Security Council were to refer the situation (art. 15 ter), Russia’s veto makes that inconceivable under the current system.

In light of this gap, it has been suggested that the Assembly of States Parties might amend the Statute via article 121 to add an additional provision allowing for the Court’s jurisdiction to be triggered by a referral by the UN General Assembly under the Uniting for Peace resolution. As a matter of jurisdictional authority, such an option would share many of the features of a tribunal endorsed by the General Assembly, as discussed below.

Putting the ICC to one side, the second possibility is an international tribunal created for the specific purpose of trying aggression. There are reasons to be skeptical about the coercive authority of the UN General Assembly to create such a tribunal on its own initiative. Whereas the Security Council has created tribunals unilaterally pursuant to its power to order non-forcible coercive measures under article 41 of the UN Charter, the General Assembly has no clear coercive authority equivalent to that provided in article 41. It is in part for that reason that it decided instead to create a non-coercive investigative mechanism when Security Council action on Syria became impossible.

This leaves two alternative possibilities for the creation of an international tribunal. First, it could arise from the pooled universal jurisdiction of states generally. Second, as a hybrid tribunal, it could arise from the territorial jurisdiction and consent of Ukraine, where aggression is proscribed in article 437 of the criminal code. The legitimacy of either effort could be bolstered considerably by the endorsement of the General Assembly (along the lines provided to the Extraordinary Chambers in the Courts of Cambodia). Moreover, that endorsement may be important in characterizing the court as acting on behalf of the broader international community. However, such a tribunal would not be rooted in the General Assembly’s coercive or other legal authority. Ultimately, the authority of either tribunal would be derivative of the underlying jurisdictional authority of the states involved.

Starting with states’ territorial jurisdiction, aggression is criminal under the domestic criminal codes of the Russian Federation (art. 353), Belarus (art. 122), and Ukraine (art. 437). Indeed, Ukraine was the forum for such a trial in 2015-2016—a case that relied upon the aforementioned lack of a leadership restriction to prosecute two ex-members of the armed forces of the Russian Federation for aggression-related crimes arising from their participation in the ranks of the self-proclaimed Luhansk People’s Republic in 2015.

Legally, the primary obstacles to Ukraine’s territorial jurisdiction would be immunities and the related principle of par in parem imperium non habet (the principle that states cannot stand in judgment of one another). I have argued elsewhere that the latter problem is overstated. However, the immunity obstacle is more significant. As discussed below, an international tribunal bolstered jurisdictionally by Ukrainian consent may have a significant advantage over the domestic courts of Ukraine in this respect.

The option of universal jurisdiction poses a different challenge. By a recent estimate, approximately twenty states provide for universal jurisdiction over aggression in their domestic law. Interestingly, Belarus is one of those states, so it would have little standing to complain about the assertion of such jurisdiction over Lukashenko. However, this is a small group of states and it cannot be denied that a unilateral universal jurisdiction prosecution for aggression would generate controversy (para. 5). Here, too, an international tribunal may have a legitimacy advantage. The limited number of states currently asserting universal jurisdiction over aggression in their domestic law would not preclude a broad number pooling their jurisdiction in this case. There is no clear international law obstacle to the assertion of such jurisdiction over an international crime (para. 45). Whether or not states have incorporated that authority into their domestic law, they could pool that latent universal jurisdiction now through the passage of new legislaton. The crime’s pre-existing customary status would be sufficient to address any issues regarding retroactivity (art. 15(2)).

The IMT, of course, adopted a model of pooled jurisdictional authority, holding that the states involved did “together what any one of them might have done singly” (p. 461). However, in that context, their individual (and thus collective) authority to do so was understood to be grounded not in universal jurisdiction, but in their “sovereign legislative power” in light of Germany’s unconditional surrender and the ensuing right of the victors to “legislate for the occupied powers,” at least insofar as doing so entailed expressing “international law existing at the time of its creation” (p.461). At the same time, it is worth noting here that it was Soviet jurist Aron Trainin who played a crucial role in laying the conceptual foundation for the prosecution of aggression at Nuremberg and who did so envisaging the creation of a “special international tribunal,” as also advocated by Soviet Foreign Minister Vyacheslav Molotov.


Each of these avenues will confront the issue of immunities. Aggressive war is, by definition a state act (art. 8 bis(2)). As such, prosecution outside of the national courts of the accused could implicate both functional immunities, applicable to all state officials for acts undertaken in their official capacity, and status immunities, applicable to sitting heads of state, heads of government, and foreign ministers. Because functional immunity inheres in the official nature of the act, it endures beyond the individual’s status as an official. Status immunity, on the other hand, inheres in the current status of the individual as head of state, head of government, or foreign minister, and lapses with the cessation of that status. Either kind of immunity may be waived by the state to which it attaches. It has also been argued that the UN Security Council may preclude the viability of such immunities (see also paras. 119, 149).

As discussed above, prosecution before the ICC would require Security Council referral or (arguably) the ad hoc acceptance of Russia and Ukraine. In light of the ICC Statute’s position on the “irrelevance” of official capacity and the inapplicability of immunities for states parties (art. 27), either of these paths to ICC jurisdiction would avoid any immunity obstacles through waiver or Security Council authority. However, given the extremely low likelihood of that scenario, the key question is how to understand the role of immunities before a foreign domestic court or an ad hoc international tribunal that does not have the consent of Belarus or Russia.

Functional immunity

Much of the focus thus far has been on status immunities. However, functional immunities are of even greater importance here. The majority of those potentially liable for planning, preparing, initiating, or waging aggressive war are not protected by status immunities. The latter protects the head of state, foreign minister, and likely very few if any others. Moreover, even the foreign ministers and heads of state who are shielded by status immunity will lose that shield upon leaving office.

A common view is that functional immunities are simply inapplicable to the prosecution of international crimes. This view is widely, although not universally, accepted for war crimes, genocide, crimes against humanity, torture, and enforced disappearance, as reflected in the work of the International Law Commission (ILC). There is more controversy on the applicability of this exception to aggression. Indeed, pursuant to the 2016 recommendation of Special Rapporteur Concepción Escobar Hernández (para. 222), the ILC refrained from including aggression on its draft list of crimes to which official immunities do not attach. This was the subject of disagreement within the Commission, with some members insisting that the ILC would be “remiss” not to recognize the nonapplicability of functional immunities to aggression, particularly given that it entails “the most serious and dangerous form of the illegal use of force” and is necessarily “committed by State officials as an act performed in an official capacity” (para. 241). Conversely, ILC members who supported the exclusion of aggression emphasized that the ICC amendment incorporating the crime had yet to enter into force (para. 242), a reality that has since changed. It is also notable that the Rapporteur’s report explained the exclusion of aggression from the list by referring to the Commission’s prior statement that “the crime of aggression must be entrusted primarily to international courts and tribunals, given the political implications it could have for the stability of relations between States” (para. 222). It is plausible that this line of reasoning entails that an international tribunal would not be bound to recognize such an immunity.

Regardless of the Rapporteur’s line of reasoning, functional immunity would logically appear to be out of place in the context of an international crime that is by definition a state act. Certainly, the applicability of such an immunity before domestic courts would make sense only if there are alternative fora for the prosecution of the crime. As the ILC debate indicates, an international court offers the most plausible solution to that problem. The broad endorsement of such a court by the General Assembly could go a long way toward settling customary law on this issue.

Status immunity

Of course, even assuming functional immunity poses no obstacle to prosecution, it is clear that Putin would be at the top of the list for any prosecutor and that his immunity is more robust, as long as he remains head of state. In contrast to the non-applicability of functional immunities, the International Court of Justice held in 2002 that status immunities obtain before foreign domestic courts, even in cases implicating international crimes (para. 58).

There are three ways that this obstacle might be overcome. The first and most obvious is that the immunity will lapse as soon as Putin ceases to hold a protected position. Whether and when that will occur is unclear, but it is worth noting in this respect that statutes of limitations are not generally applicable to international crimes (as is reflected in the case of aggression in the criminal codes of Russia [art. 78] and Ukraine [art. 49]).

Second, it has been suggested that Ukraine’s right to self-defense might itself entail the right to override legal immunities to that end (at 41:20). The thought here is that if Ukraine can use force to defend itself, including even by overthrowing the aggressor regime if necessary to repel the aggression, it must also be able to arrest and detain the leader on that basis. Indeed, detaining the commander-in-chief of the adversary would appear to be straightforwardly authorized under international humanitarian law (art. 21). Once detained, it might be thought, he could be prosecuted for international crimes before the detaining state’s own courts or in an international court acting on the basis of its consent. Quincy Wright offered an argument along these lines shortly before the Nuremberg prosecutions (p.278). The most obvious difficulty with this line of reasoning, as Wright recognized, is that it would seem not to apply after the war ends to any leader who remains in office (p.278). Given the challenges associated with gaining custody over Putin during the war, this caveat is essentially debilitating as a practical matter.

Third, drawing on ICJ reasoning in the ruling on immunities before domestic courts (para. 61), both the Special Court for Sierra Leone (paras. 52-53) and the ICC (para. 113) have now held that status immunities do not apply to the prosecution of international crimes by international courts, because the latter function on behalf of the international community, rather than on behalf of specific states (para. 115). To be sure, this theory is controversial (e.g. here, here, here, but see here). However, the very fact of its repeated assertion by international authorities gives it weight. Broad state support for an ad hoc tribunal in this instance could itself help to clarify the state of the law on this issue.

If international and domestic courts are to be treated separately in this respect, a threshold question is how many states need to be involved for an ad hoc tribunal to qualify as genuinely international. It is here, rather than in providing authority for the tribunal, that the support of the UN General Assembly may be most important, given the body’s breadth of membership. If it is correct to say that status immunities do not apply before international courts qua international courts, a court created by the General Assembly would have the strongest claim to that status.

The Policy Wisdom of Such Efforts

Beyond the complexity posed by the legal grey areas discussed above, several additional concerns regarding the wisdom of pursuing an ad hoc aggression tribunal have been raised in the week since it was first proposed. Some have been articulated by Kevin Jon Heller in a robust Opinio Juris post opposing the creation of the tribunal. Two are worth emphasizing here: the allocation of resources and the problem of selectivity.


On the issue of resources, several specific concerns might be raised. The tribunal will be costly; it will involve the prosecution of only a small number of individuals; it will compete with the ICC for resources and cooperation; it will be difficult to gain custody over the accused; and, if political conditions change sufficiently to allow for custody and prosecution, that could be performed at the ICC or in the domestic courts of Ukraine, rendering any ad hoc tribunal redundant. These are genuine concerns and they caution against establishing such a tribunal without careful reflection. It may be that a better use of resources at this stage would be to establish and fund an investigative mechanism, with a view to facilitating accountability in whichever fora become viable down the road. At the same time, there are countervailing factors worth considering.

First, it is true that accountability will depend on political conditions. However, even when conditions become propitious, it is not obvious that prosecution before the ICC or domestic courts will become viable. As noted above, article 12(3) may not be available for aggression. A Security Council referral could solve this issue, but it would not be contingent solely on Russian approval. All five permanent members would have to acquiesce, and some may worry about precedent. An ICC Statute amendment addressing the flaws in the jurisdictional regime for aggression would be desirable, but it is unclear whether it would have retroactive effect and it is unlikely to be pursued in the short term. Domestic courts, including those in Ukraine, may be available, but the challenges they would face regarding immunities, par in parem imperium non habet (“equals have no sovereignty over each other”), and possible charges of victor’s justice are particularly acute. An international tribunal would be better positioned on those fronts and it may be that now is the moment at which the political will for its establishment is greatest. It is also notable that Ukraine itself has requested the creation of such a body.

Second any such tribunal might appropriately be structured with an “accordian system” of staffing and resource allocation, along the lines of the Residual Mechanism for International Tribunals. Early on, the focus would be on beginning investigations and sorting evidence. At a certain stage, it may shift primarily to evidence preservation, recognizing that arrest warrants may take time to yield results. In that period, the tribunal could contract, with the readiness to expand once individuals become available for trial, as occurs if long-standing fugitives are brought before the Resdiual Mechanism. To structure the tribunal in such a way would avoid the defeatism of assuming that conditions will never be propitious for accountability, while eschewing the utopianism that could lead to the construction of a fully-functioning court with no defendants. In the intervening period, arrest warrants would both serve their own condemnatory function and constrain significantly the travel of those charged.

Third, much of the violence inflicted in an aggressive war and the human suffering that it causes will not be covered by war crimes or crimes against humanity. The wrongfulness of that violence is precisely why aggression is a crime. On an expressive level, the ICC investigation is inherently deficient in not being able to reach those wrongs.

Fourth, even if the number of persons responsible for aggression across the Russian and Belarusian regimes were not to reach the 39 convicted at Nuremberg and Tokyo, it is not unrealistic to think that the number would exceed the 13 charged with core crimes before the Special Court for Sierra Leone—a relatively successful example of a hybrid court. Few of those individuals is likely to be straightforwardly criminally responsible for war crimes or crimes against humanity perpetrated in the conduct of the war.

Fifth, other situations have been the focus of multiple international and hybrid tribunals, as well as multiple domestic proscutions. It is possible for such bodies to function in parallel without institutional conflict and redundancy. Universal jurisdiction efforts relating to Syria have exemplified the possibility of coordination and mutual reinforcement across jurisdictions (p.310).  Cooperation between the ICC and the Special Criminal Court for the Central African Republic may also provide useful lessons learned here.


A second concern is that of selectivity. Here, two issues may be distinguished. The first is the failure to have prosecuted aggression at the international level in any case since World War II, despite the fact of numerous illegal wars during the intervening decades. The invasion of Iraq in 2003 has appropriately been raised as a particularly galling precedent in this respect.

The failure to hold accountable those who have waged such wars is lamentable. However, the revival of the crime of aggression has to begin somewhere. The invasion of Ukraine, as one of the most blatantly aggressive wars in the past 80 years, offers an opportunity to begin that revival.

A second dimension of selectivity is more problematic. For it is not just that past aggressions have been left unscrutinized. The more problematic reality is that some of the states that may support the proposed tribunal lobbied actively for the curtailment of the ICC’s jurisdiction over the crime (with the consequence of rendering it unavailable in the present case), have declined thus far to ratify the Court’s aggression amendment (thus exempting themselves from its application), and stand accused of waging aggressive war in the not-too distant past (Iraq being the most obvious example). The problem of hypocrisy does not preclude the legal viability of the proposed tribunal, especially given Ukraine’s role as a driving force behind the initiative, but it would call into question the tribunal’s moral standing to issue the kind of condemnation that is supposed to inhere in international criminal punishment.

The proposed body must address that problem. Optimally, it would be created as a standing tribunal, available for the prosecution of aggression beyond the current situation. Of course, in that case, the aforementioned proposal to amend to the ICC Statute may be a more efficient option. Even if such options are eschewed, the effort toward an ad hoc tribunal should be driven by the support of states that have ratified the ICC aggression amendments or incorporated the crime of aggression into their national criminal codes. Furthermore, any General Assembly involvement ought to involve a call for states to pass legislation providing for the incorporation of aggression into their domestic criminal codes and for all ICC States Parties to both ratify the aggression amendment and seek to amend the ICC Statute so as to eliminate the unique jurisdictional restrictions attached to aggression.

The aggression against Ukraine is clear. It provides an opportune moment for the revival of a neglected atrocity crime. But the charge of selective justice will ring true unless the states involved in facilitating accountability for it demonstrate with more than just words that they are ready to be held to the same standard.


Phot credit: Russian President Vladimir Putin chairs a meeting with members of the Security Council in Moscow on February 21, 2022 (Alexey Nikolsky/Sputnik/ AFP via Getty Images)