The idea was floated by EU chief Ursula von der Leyen on Wednesday in a video statement. “We are ready to start working with the international community to get the broadest international support possible for this specialized court,” von der Leyen said.

An investigation into alleged war crimes and crimes against humanity committed by Russian troops in Ukraine has been launched by the International Criminal Court (ICC) since the early days of the Russian invasion of Ukraine, but the court has no jurisdiction to prosecute crimes of aggression—like Russia’s invasion.

An act of aggression is defined by the United Nations as the “invasion or attack by the armed forces of a state of the territory of another state, or any military occupation.”

A special tribunal would be able to hold Russia’s top officials accountable for the alleged war crimes committed in Ukraine in the past nine months and the crime of aggression, unlike the ICC.

“Russia must pay for its horrific crimes, including for its crime of aggression against a sovereign state,” von der Leyen said. “This is why, while continuing to support the International Criminal Court, we are proposing to set up a specialized court backed by the United Nations to investigate and prosecute Russia’s crime of aggression.”

British law professor and author Philippe Sands, who had suggested the creation of a special tribunal for Ukraine days after Russia’s full-scale invasion of its neighboring country, said that the EU’s announcement is “a very significant political statement” which “first and foremost, it’s indicating that the crimes committed by the top table are of more rather than less significance.”

By “top table,” Sands means that the crime of aggression that Russia committed against Ukraine is the responsibility of the Russian top officials alone: “those who participated in the decision to invade Ukraine and to continue the invasion.”

They include Putin, foreign minister Sergey Lavrov, the main generals of the Russian army, and potentially even those who financed the war.

The first way to hold the Russian leadership accountable, Sands told Newsweek, is “to establish an interim mechanism and appoint an interim special prosecutor to investigate the facts [around the crime of aggression].”

On the basis of that investigation, Sands said, the special tribunal should decide which individuals to prosecute based on the applicable law, as this would be easier to do than identifying individuals responsible for war crimes or violations of human rights.

“It takes you straight to the top table, that’s the absolutely crucial point. With war crimes and crimes against humanity, it’s extremely complex to link people on the top table with individual actions taken in Bucha or in other places. With the crime of aggression, as in Nuremberg, you go straight to the top,” he said.

The special tribunal the EU is pushing for would be the first to deal “explicitly” with the crime of aggression since the Nuremberg trials held between 1945 and 1946.

The legal consequences of creating this tribunal will only become clear over time, said Sands, as that depends on what mechanism is established and how the special tribunal will operate.

But there are several challenges facing the initiative.

“There are political challenges getting support. There are practical challenges—how do you get hold of the defendants if they are indicted?” said Sands. “And there are legal challenges in relation to, for example, claims of immunity, but that would be very limited. Essentially, you’re just talking about the president, the foreign secretary, the foreign minister, and the defense minister—very hard for anyone else to claim immunity.”

None of these practical, political or legal difficulties stand in the way of establishing such a tribunal, according to Sands, but the initiative also has another potential benefit.

“It creates an incentive for some of those who are around Putin to peel away to avoid investigation or indictment. That is what happened in 1945 with the creation of Nuremberg. Various top Nazis started to cooperate with the Allies to avoid being indicted.”

Russia has until now denied targeting civilians and committing any war crimes in Ukraine. Officially the war is still referred to as a “special military operation” in Russia, as per the Kremlin’s law.