In an unprecedented move, thirty-nine states have requested that the International Criminal Court (ICC) investigate atrocities committed in Ukraine. It is a welcome and important development. But one crime that the ICC will not be investigating is the crime of aggression, despite Russia’s invasion of Ukraine is a textbook example of a criminal invasion. Why? Because the crime’s definition was neutered by Western states. States that handicapped the ICC’s ability to investigate aggression have a special responsibility to step up to the plate and help to achieve justice for atrocities.

The word aggression is on the tips of the tongues of diplomats and observers describing events unfold in Ukraine. For many, the illegal invasion of Ukraine by Russian forces clearly fits the bill of an illegal, aggressive war. It was for exactly these kinds of situations that the ICC was given jurisdiction over the crime of aggression under the Rome Statute. But when states negotiated its definitional contours, they left it a largely impotent shell of its potential self.

Over a decade of contentious negotiations over the contours of the crime of aggression, the likes of Canada France, the UK, and Japan, sought to severely restrict the definition of the crime. Noah Weisbord, a Canadian law professor who has written a book on the subject has observed that Canada’s position, for example, was viewed by other states as providing “avenues for rogue leaders to use force as they please”.

The result of the negotiations was two troubling requirements that curtail the ICC’s jurisdiction: one, the Court could only investigate the crime of aggression if both states – the aggressor and the invaded party – were members of the Court, and two, if ICC member-states “opted-in” and accepted jurisdiction over the crime of aggression.

Even if Kyiv decided to join the ICC tomorrow, the Court could not investigate the crime of aggression in Ukraine. The only way for the ICC to be able to initiate such an investigation would be if the United Nations Security Council referred the situation in Ukraine to the Court. But with Russia sitting plum on the Council with a veto in its back pocket, that’s not going to happen.

Given its involvement in watering down the crime of aggression, those states that neutered the definition of aggression under the Rome Statute have a special responsibility to address other international crimes being committed in Ukraine, including war crimes and crimes against humanity.

The referral of Ukraine to the ICC is a good first step. The decision matters, because without a member-state of the ICC like Canada or Lithuania referring Ukraine, the Court’s Prosecutor, Karim Khan, would have to undertake the cumbersome process of asking judges in The Hague to authorize the investigation. Put otherwise, the move saves the Prosecutor some time and expedites the investigation. According to Khan, a team of investigators was already on its way to Ukraine last week.

But more can be done. Governments should consider putting money where its proverbial mouth is.

With Western states now actively sending the ICC Prosecutor jobs, they should abandon their position that the Court’s budget should be effectively frozen and consider making voluntary contributions to the ICC’s work. This is not unprecedented. Amidst allegations of genocide, in 2005 the Canadian government of Paul Martin contributed $500,000 to the ICC to support its investigation into atrocities committed in the Darfur province of Sudan.

States can and should likewise encourage the UN General Assembly to create a body to collect and preserve evidence of atrocities committed in Ukraine. The General Assembly has previously done just that for both Syria and Myanmar. States could help with the funding and training of such an institution. They could also explore the possibility of making such a mechanism a permanent institution rather than having to re-invent the wheel each time atrocities demand it. While the likelihood that Putin or members of the criminal enterprise he runs out of the Kremlin will be brought before judges on charges of war crimes are slim right now, when the opportunity arises, it will be crucial that the relevant evidence can be marshalled.

States should also declare openly that they are willing to follow its European partners and exercise universal jurisdiction over anyone alleged to have perpetrated atrocities in Ukraine. Some states are leaders in this respect. Others, like Canada, are laggards. Instead of prosecuting them, Canadian authorities seek to deport alleged war criminals to the very situations where the atrocities were committed, with no guarantee that accountability will be pursued. To be sure, Putin may never travel to Western capitals again. But others involved in atrocities might, and governments should commit to prosecuting them if ever they do.

Finally, states should consider funding a sophisticated support programme aimed at bolstering the capacity of Ukraine’s domestic justice system to investigate and prosecute international crimes. The country has jurisdiction over the crime of aggression. It is often said that the future of international criminal justice is domestic. While the ICC’s role is important, funding, supporting, and training Ukrainian investigators and prosecutors would pay greater dividends than, say, establishing a new tribunal focused exclusively on aggression.

Many of the states that referred Ukraine to the ICC present themselves as global leaders on international justice. But there have been times, as with negotiations over the crime of aggression, where they have done more to frustrate than further global accountability efforts. If states like Canada, the UK, France and others want to prove that that was just an aberration, seeking justice for atrocities in Ukraine would be an opportune moment to do just that.