Ukraine's parliament has urged the international community to establish a special international tribunal for the crime of Russian aggression against Ukraine. In an interview with DW, Claus Kress, an expert on international law at the University of Cologne in Germany, explains how such a tribunal would work, why it doesn't necessarily need Russia's consent, and why a conviction of Russian President Vladimir Putin is not required as a matter of course.

DW: What would this international special tribunal be about?

Claus Kress: The special tribunal would deal with the accusation of aggression. That is very important for Ukraine because it concerns the accusation of war per se. From Ukraine's very understandable point of view, setting in motion the war of aggression is the "original sin" that paved the way for the countless atrocities committed during the war — the war crimes.

How likely is the establishment of a special tribunal in Germany?

Germany, like several other states, has not yet made a commitment, which is hardly surprising given the fact that there are a number of legal and political issues to be clarified, and they are not simple. The talks have recently gained significant momentum, but I am not in a position to say when they will be concluded.

What would the establishment of a special court look like in practice?

Various models are currently being discussed. The preferable model from my point of view has two steps, the first being a United Nations General Assembly resolution. One would have to secure the necessary majority in advance. It would be very unfortunate, not least from Ukraine's point of view, if such a vote were to fail in the General Assembly.

Unlike the United Nations Security Council, the General Assembly cannot establish an international criminal court, but it can, on behalf of the United Nations, express the desire of the international community to do so. That would be of utmost importance concerning the legitimacy of such a tribunal.

Then the UN Secretary-General could conclude an international treaty with Ukraine on the establishment of the tribunal.

How long would that take?

Criminal proceedings are a complex process. The first step involves the initiation of investigations, which means securing evidence and, if that holds up, determining who stands accused and giving a precise explanatory statement concerning the respective accusations. That in itself is a very demanding process. The crime of aggression is firmly anchored in customary international law, but so far there have been very few international proceedings. The proceedings before the military tribunals in Nuremberg and Tokyo after World War II are significant precedents to this day. So any step in criminal proceedings on suspicion of aggression would have to be particularly well considered. One should not expect a high-speed trial.

However, even the initiation of investigations by an international criminal court would send the immensely important message that the international community takes even the suspicion of a crime of aggression extremely seriously; that it attaches no less importance to it than to the accusations of war crimes, crimes against humanity and genocide over which the International Criminal Court exercises its jurisdiction in the Ukraine situation.

Would the war have to be over before trials could get underway?

In the case of Nuremberg and Tokyo, but also in the case of most of the trials before the International Criminal Tribunals for the former Yugoslavia and Rwanda, the hot phase of the conflict was already over. But in principle, trials are possible before the end of the war — the situation changed with the establishment of the International Criminal Court (ICC) in 2002. That court is a permanent institution and can become active within the scope of its jurisdiction as soon as suspicions arise.

What problems does the international criminal justice system face concerning arrest warrants and indictments?

The crime of aggression is a leadership crime. So it is about the criminal responsibility of Russia's political and military leadership, headed by President Putin. However, the key practical challenge is the same one that applies to the International Criminal Court: Russian defendants who are on Russian territory are inaccessible as long as the current regime remains in power.

Let's say there is no change in the regime until after Putin's death, wouldn't it all have been for nothing?

No. Of course, the Russian president is at the center of the accusations, at least of the accusation of the crime of aggression. But President Putin is not the only suspect. Concerning systematically committed war crimes, crimes against humanity and genocide, there are typically main perpetrators at the top of the respective system of injustice, but also those responsible at subordinate levels of the hierarchy, and then those who commit the atrocities on the ground. Suspicion is by no means directed against just one person.

Also, I would like you to consider that of course, if the perpetrator is found guilty, the meaning of criminal proceedings is only fulfilled in its entirety in a conviction and execution of the sentence. But the very start of an investigation is a signal to the world that everything possible is being done to investigate the suspicion of a crime under international law. Even an international arrest warrant can restrict the suspects' freedom of movement and even an overwhelming indictment can contribute to delegitimizing a state leader.

Claus Kress teaches Criminal and International Law, he is Chair of German and International Criminal Law at the University of Cologne and heads the university's Institute for Peacekeeping Law.

Interview: Olena Perepadya

This article was originally written in German.