JURIST’s Sarisha Harikrishna interviews Dr Carrie McDougall, Associate Professor at the Melbourne Law School on the prosecution of the crime of aggression under the Rome Statute of the International Criminal Court (ICC). The prosecution of the crime of aggression, enshrined under Article 8bis of the Rome Statute has gained renewed interest within the international community in light of the unfolding horrors of war in Gaza and Ukraine. Professor Dr McDougall’s distinguished body of scholarly work includes her influential 2013 publication of her book on the topic, which offers a comprehensive examination of the crime.

The crime of aggression is the use of armed force by a State against the sovereignty, integrity or independence of another State, with its definition adopted through the amendments to the Rome Statute at the first Review Conference of the Statute in Kampala, Uganda, in 2010 (known as the Kampala Amendments). Beyond her wealth of scholarship on the crime of aggression, she has also actively participated in the real-world development of these laws, having served as a legal adviser to the Australian delegation throughout the negotiations that led to the adoption of the crime’s definition at the 2010 Kampala Amendments. Her unique combination of deep academic expertise and direct involvement in the diplomatic process makes her insights into the current challenges and prospects for prosecuting aggression invaluable.

JURIST: The “manifest violation” threshold was the crucial legal compromise at Kampala. Given that modern warfare is increasingly characterized by hybrid operations and ‘grey zone’ tactics designed to fall below this threshold, does the crime of aggression risk becoming structurally incapable of addressing the main ways states undermine international peace today?

Carrie McDougall: To be very clear, we agreed on the definition of the crime of aggression in the Special Working Group on the Crime of Aggression, so but for Kampala itself, of course it wasn’t adopted until 2010 at the review conference. But really the definition was set in 2009 and you’re right, that the “manifest violation” threshold was effectively the bridge between those states that wanted the state act element of the crime of aggression restricted to wars of aggression and those states that wanted to attach individual criminal responsibility to all violations of the prohibition on the use of force. Exactly which state acts of aggression meet the “manifest violation” threshold has you know in broad terms been left to the judges of the ICC to determine.

In my own academic work on the crime of aggression, I have explained that I think based on the travaux préparatoires and my engagement in the negotiations that the intent of the threshold was to exclude acts of insufficient seriousness and acts that are not incontrovertibly a violation of the prohibition on the use of force. So I think we can say with some certainty that not all violations of the prohibition will attract individual criminal responsibility and it is important to remember that that is true of all serious international crimes. So not all violations of IHL amount to a war crime and not all violations of human rights law amount to a crime against humanity or genocide. It is only the most agreed examples where there is a collective interest that is threatened and states have decided that it is important that people should be able to be criminally prosecuted.

In relation to your specific question about ‘grey zone’, we normally understand ‘grey zone’ activity to describe conduct that doesn’t truly amount to a violation of the prohibition on the use of force. Given that it is not a clear use of force, I think you’re right to say that it is very unlikely to meet the state act on the element of the crime of aggression. But the crime of aggression was never intended to respond to all types of unlawful conduct that could threaten international peace and security. It attaches individual criminal responsibility to certain violations on the prohibition on the use of force. The other, I guess technical point that I would make is well, ‘grey zone’ activity is a growing concern. I don’t think it does represent the main way that states undermine international peace and security at the moment. You know, you would have to look at the conflicts in places like Ukraine, Gaza, Yemen or the Democratic Republic of the Congo to see that. So I think that the unfortunate reality is that in 2025, 15 years after the Kampala Amendments were adopted, the crime becomes more, rather than less relevant.

JURIST: The crime of aggression uniquely criminalizes a state act, requiring the ICC to formally determine state responsibility before individual guilt can be assigned. Does this fusion of interstate and criminal law create an insurmountable procedural hurdle, making convictions legally and politically unattainable outside of total military defeat?

McDougall: No, would be my short answer. I think the suggestion that the ICC must formally determine state responsibility before individual guilt can be assigned is factually incorrect. The ICC very clearly lacks the power to make findings in relation to responsibility, so under Article 12 and Article 25(1) of the Rome Statute, the ICC only has jurisdiction over natural persons and under Article 25(4), the statute explicitly states that no provision in the statute relating to individual responsibility shall affect the responsibility of states under international law. Yes, it is true, that nevertheless an ICC determination on the crime of aggression could reflect more generally on state conduct but this aim is true in relation to many conceivable examples of war crimes, prosecutions or prosecutions of crimes against humanity or genocide. So, establishing the requisite intent for genocide will often cause a court to look at state plans and policies assessing the widespread or systematic attack element of the crimes against humanity.

War crimes, you know, you may have to determine whether there is an international conflict, properly speaking, the court only exercises jurisdiction over war crimes where they are part of their plan or policy and where there has been a large-scale commission of war crimes. So, all of the prosecutions before the ICC could cause the court to examine governmental actions and policies. I am very firmly of the view that there is no real basis to suggest that a determination of a crime of aggression is more controversial or somehow inappropriately will require the court to examine state conduct because the same is true of all serious international crimes.

JURIST: A core philosophical justification for the crime of aggression is the protection of state sovereignty. Yet, the principle of sovereignty also provides the jurisdictional opt-outs and immunities that shield perpetrators. Is the crime of aggression therefore trapped in a paradox where the very principle it protects is also the primary obstacle to its enforcement?

McDougall: I would say first that it is important to understand that the crime of aggression is not just about sovereignty, so I think it protects not only sovereignty but also against the death and destruction that will almost inevitably accompany any crime of aggression. But I do agree that the crime is in part designed to protect not only sovereignty but also political independence and territorial integrity of states and I think they are valuable interests that deserve protection. I don’t know if I agree that sovereignty is the primary obstacle to the prosecution of aggression. You mentioned immunities, and I think in that context, it is important to recall that there’s a line of decisions, so the International Criminal Tribunal for the Former Yugoslavia (ICTY), the Special Court for Sierra Leone, the ICC have consistently held that immunities are not applicable before an international criminal court or tribunal. So at least in that context, immunities are irrelevant.

This situation is of course different if we’re talking about a domestic prosecution before a foreign court. We know that the head of state, head of government, foreign minister will enjoy personal immunity which will be an absolute bar to the issuing of an arrest warrant or any prosecution of those persons for the crime of aggression. The applicability of functional immunity enjoyed by other state officials is less clear at the moment. The International Law Commission has suggested that functional immunities do not apply to the prosecution of a serious international crime before a foreign domestic court and its revised draft, it is added that the crime of aggression is at the least of crimes to which functional immunity doesn’t apply. But I think there is real scope for debate about whether the ILC’s position represents a codification of customary international law or rather its progressive development. So, I think we will need to wait to see what courts and tribunals do with that and how states react to the ILC’s work. I have long been of the view that domestic courts are badly positioned to prosecute crimes of aggression due to a number of reasons such as being unable to secure the presence of the perpetrator, noting that by definition, only those in a position to control or direct the military or political action of a state can commit the crime of aggression. I think any domestic prosecution will struggle to be viewed as legitimate and inevitably it will be tainted by perceptions of victors justice or victims revenge and I think that frankly speaking, domestic judges are not experts in jus ad bellum (the conditions under which States may resort to war or the use of armed force in general) and the definition of the crime of aggression requires real expertise to be properly applied and so I don’t think that it should be within the purview of domestic courts. Understandably, states will want to retain discretion to prosecute their own nationals accused of committing the crime, but otherwise I think there are good policy reasons for making sure perpetrators are prosecuted on the international level where immunities don’t apply.

JURIST: The Kampala compromise on jurisdiction was a necessity to secure state buy-in. But in conflicts like Ukraine, where non-state actors who are not party to the Rome Statute is the clear aggressor, the Court’s jurisdictional constraints prevent action. Does this illustrate that, while diplomatically successful, the regime’s design has created a Court institutionally paralyzed when major powers engage in aggression?

McDougall: Yes, the definition of the state act element of the crime does leave room for debate about exactly which acts are covered, but I think it’s beyond doubt that Russia’s invasion of Ukraine and its ongoing use of force against Ukraine’s sovereignty, political independence and territorial integrity is quite clearly a state act of aggression and that’s being widely recognized by the majority of states and almost unanimously recognized by jus ad bellum experts. You then have the purported annexation for oblasts of Ukraine which would be another archetypal act of aggression, which you know fairly uncontroversially would meet the definition of the state act element of the crime. The debate is not about whether the crime is being committed, the questions are about who, who would satisfy the individual conduct element of the crime and of course the real issue is jurisdiction.

So, your question raises lots of different issues. The provisions governing the ICC’s jurisdiction over the crime of aggression are really complex. It’s a tailor-made regime that gives the ICC jurisdiction over a far narrower range of situations compared to its jurisdiction over the other crimes and that’s a direct result over the position of the permanent five members of the UN Security Council (UNSC) and a position that was reluctantly accepted by ICC state parties as the price for criminalizing aggression and the amendments in Kampala. Jurisdictional provisions are complex and proper interpretation remains contested, but those unresolved debates I think are a bit moot in the Russia-Ukraine context, because it is very clear that the ICC cannot investigate or prosecute any crime of aggression committed on a non-state party’s territory or by a non-state party national, absent a security council referral which is obviously not going to of course be coming in in the Russia-Ukraine context due to the veto.

Russia is of course not an ICC state party and until the 1st of January 2025, Ukraine wasn’t a member either. Ukraine had filed two ad hoc declarations accepting the Court’s jurisdiction back to late 2013 but that opt-in mechanism isn’t sufficient to enliven the Court’s jurisdiction over aggression. Yes, the ICC lacks any jurisdiction over any crime of aggression committed in the Russia-Ukraine conflict and that is of course a really significant departure from the ordinary jurisdictional regime of the ICC where the Court’s jurisdiction has typically been accepted by the state on whose territory a crime has been committed or by the state of nationality of the alleged perpetrator. And so, I think you’re absolutely right that the Russia-Ukraine conflict has really highlighted how unfortunate it is that states restricted the ICC’s jurisdiction by way of aggression because it can’t help enforce the prohibition on the use of force and I think it sort of shows that this is very clearly the result of politics and reflects a double standard. Of course, to focus on solutions, that’s why together with other small group of experts have been actively supporting the government of Ukraine in finding or in working towards establishing an ad hoc tribunal to find that those responsible for the crime of aggression committed on Ukrainian territory will be held accountable.

So, you might be aware that an agreement has now been concluded between Ukraine and the Council of Europe and this will establish an ad hoc tribunal with jurisdiction over the crime of aggression and that tribunal will become operational as soon as a sufficient number of states have pledged political and financial support for the tribunal. In order to reduce concerns about selectivity and I guess more importantly, to make sure we don’t face the same bar to ICC action in relation to future crimes of aggression, in parallel there’s been a big push to amend the ICC’s jurisdiction over the crime. That was also the principle of model amendments that were prepared by the global institute for the prevention of aggression. Those amendments were formally tabled by groups of states and champions by the Assembly of States Parties (ASP), and you’re probably aware of this, but we met in July to enable the ASP to consider the amendments. Unfortunately, they were opposed by a small group of states, which are the UK and France, which meant that the amendments could not be adopted. In recognition of the importance of aligning the Court’s jurisdiction over aggression with its jurisdiction over other crimes, the ASP did agree to consider the amendments again in 2029 with an interim meeting to be held in 2027