Putin’s use of military force against Ukraine is crime of aggression

President Vladimir Putin’s decision to launch attacks on Ukraine poses the gravest challenge to the post-1945 international order, one premised on the idea of a rule of law and principles of self-determination for all peoples and the prohibition of the use of force.

It is not the first time that Russia has taken a military interest in the territories it now seeks to occupy: in September 1914, Russia occupied the city of Lviv, causing tens of thousands to flee westward, including my ten-year-old grandfather.

The Soviet Union returned in September 1939 for a second bite, and then again in the summer of 1944, remaining in control until Ukraine achieved independence in 1991.

The use of Russian military force in these areas is therefore not unfamiliar, although for Europeans who have lived for three generations without experiencing it on such a scale, last week’s events have been a shock.

History does not just go away, and memories are easily reignited. One of the differences today is that rules exist to protect us from such actions, reflected in the Charter of the United Nations, the closest thing we have to an international constitution. It is the Charter’s most significant commitments that Putin has shredded.

His televised speech offered a set of fanciful reasons for the invasion: a Greater Russia, a fake Ukraine, a Nazi Ukraine, a genocide being committed against ethnic Russians, etc.

The claims are familiar, of the kind that motivated the 1938 Nazi playbook on Munich and Slobodan Milosevic’s hopes for a Greater Serbia.

Putin has gambled, hoping that the west will blink. Following its own failures, including an illegal, failed war in Iraq, and the recent collapse of political will in Afghanistan, along with the embrace of oligarchical money and dependence on Russian gas, he hopes that the west doesn’t have the stomach to stand up to his actions.

He may be right, but his bet poses a grave challenge, and one that sanctions and financial measures alone cannot address.

Much more is needed, and it is needed fast. In the face of so flagrant a violation of the rules, it is lawful to act jointly to protect Ukraine and the fundamental rights of its people, by offering military hardware, taking steps to prevent Russia from using air power and, ultimately, putting boots on the grounds to enforce safe areas and draw lines that Russia must not be allowed to cross.

There is, too, the matter of criminality, even if I am not starry eyed about such labels. Putin’s use of military force is a crime of aggression, the waging of illegal war, an idea that originated at Nuremberg as “crimes against peace”.

Horrific images appear to show the targeting of civilians, which is a war crime, and may well also be a crime against humanity (a legal concept with origins which, like the term genocide, may be traced to the city of Lviv).

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The International Criminal Court — a child of the Nuremberg Tribunal — has jurisdiction over some of these crimes (war crimes and crimes against humanity, but not the crime of aggression) committed on the territory of Ukraine.

Russians are subject to its jurisdiction, and being president does not confer immunity. The ICC prosecutor, Karim Khan, has the power to open a formal investigation and, if the evidence supports and the judges authorise, to proceed to an indictment and prosecution.

The ICC has a gap, however, as its jurisdiction does not yet extend to the crime of aggression perpetrated on the territory of Ukraine. Why not create a dedicated international criminal tribunal to investigate Putin and his acolytes for this crime?

After all, it was a Soviet jurist, Aron Trainin, who did much of the legwork to bring “crimes against peace” into international law. As Francine Hirsch has noted in her book Soviet Judgment at Nuremberg, it was largely Trainin’s ideas that persuaded the Americans and the British to put “crimes against peace” into the Nuremberg Statute and the indictments against the German defendants.

Putin knows all about Nuremberg: his older brother died in the Leningrad siege at the age of two, and he seems to be something of a defender of the famous 1946 judgment.

Three years ago he castigated the European Parliament for challenging the Tribunal’s conclusions, to the effect that it was the 1938 “Munich Betrayal” that brought so much horror, allowing Czech territories to be annexed in the forlorn hope of appeasing Hitler.

There can be no appeasing of Putin. Chechnya, Georgia, Crimea and now all of Ukraine. On it goes. Let him reap what he has sowed, including the legacy of Nuremberg. Investigate him personally for this most terrible of crimes.

Sands is professor of law at University College London