As evidence of atrocities flood the airwaves, calls are growing for President Putin and other Kremlin officials to be put on trial at the Hague. Yet can trials begin before a war is won?

Ukrainian forces liberated the environs of Kiev over the weekend, discovering ghastly remnants of the Russian occupation at Bucha, Hostomel, and other suburbs of the capital. 

Some 300 bodies, officials report, were discovered in a mass grave at Bucha. Videos have been circulated showing decapitated bodies, some with hands tied behind their back, that are said to be civilians. Women have documented cases of rape by Russian soldiers. Looting by the fighters is widely reported. 

“I don’t know what law and what imprisonment will be adequate for this,” President Zelensky told CBS News this morning.  

“Appalled by atrocities in Bucha and other towns in Ukraine,” Britain’s foreign secretary, Liz Truss, wrote on her Twitter account. “Reports of Russian forces targeting innocent civilians are abhorrent. The UK is working to collect evidence and support @IntlCrimCourt war crimes investigation. Those responsible will be held to account.”

Will they?

The International Criminal Court was created at the turn of the century as a global venue to try charges involving crimes against humanity, war crimes, and genocide. As Ms. Truss suggests, the ICC would be the ultimate venue to try anyone suspected of the atrocities widely documented in Ukraine. 

Except the ICC’s jurisdiction applies only to countries that have ratified the Rome treaty that established the court, and Russia and Ukraine have not. Another option would be a United Nations Security Council resolution that would send a case to the ICC. As Russia has veto power at the council, such a resolution is all but impossible to achieve. 

The ICC nevertheless believes it can start the trial process, as a few years ago Kiev granted the international court jurisdiction over its territories, even though it is not an ICC member. Based on Ukraine’s permission, “I have confirmed that there is a reasonable basis to proceed with opening an investigation,” the ICC prosecutor, Karim Khan, said late last month.

In addition to allegations of possible crimes that are already being investigated at the Hague, Mr. Khan added, his office will probe “any new alleged crimes falling within the jurisdiction of my office that are committed by any party to the conflict on any part of the territory of Ukraine.”

Yet, an investigation is merely the first part of bringing criminals to justice. Then there is the question of an actual trial. If the ICC prosecutor ever wants to see Vladimir Putin in his courtroom, he would need to issue an arrest warrant and then rely on cooperation from Rome Statute signatories. According to the statute, no trial can be conducted in absentia.

In one famous case, the ICC issued an arrest warrant in 2010 against Sudan’s president, Omar al Bashir. The UN Security Council sent his case to the Hague even though three of its permanent members — America, Russia, and China — are non-ICC members. Mr. al Bashir was accused of several crimes related to the genocide in the Darfur region. 

By the time Mr. al Bashir was ousted, nearly 10 years after his arrest warrant, he had traveled to several world capitals, including those of ICC members, visiting Egypt, some of the Gulf states, South Africa, and Russia. His hosts received him with all the pomp reserved to heads of state. None arrested or sent him to the Hague.

Only after Mr. al Bashir was ousted was he indicted in Sudan on corruption charges. Yet, Khartoum declined to send the former strongman over to the Hague to be tried on charges that included genocide.  

Beside the ICC, several European countries employ what is known as universal jurisdiction, which allows local arrests and trials based on alleged war crimes. Yet, Mr. Putin rarely travels outside of Russia, so the chance of him standing trial based on universal jurisdiction is slim. 

The ICC has long been accused of going after African war criminals while ignoring “white” ones. Mr. Putin would therefore be a perfect target. Because he is unlikely to ever reach the Hague, though, accusations will only grow that the court — like the rest of the UN-based international system — is biased against small players and allows a lot of leeway to the strong. 

As in Mr. Al Bashir’s case, the only realistic venue to try Mr. Putin, his defense minister, Sergey Shiygu, or his foreign minister, Sergei Lavrov, would be Russian courts. For that to happen, though, they must first be toppled, perhaps in the aftermath of a humiliating war loss.