Daniel Thurer, a Swiss jurist and scholar of international law at the University of Zurich, wrote in a 2011 book: “Wars have always been fought in accordance with certain norms.  It is one of the astonishing facts of history that, to a great extent, wars were not chaotic affairs – despite outward appearances to the contrary – but governed by rules.”

The simplest definition of “war crimes” has always been this: a violation of the international law of war that has been made into a punishable crime. But that somewhat circulatory formulation is only the beginning of the pursuit of what that phrase does mean, or should mean.

Professor Thurer’s quotation appears in a comprehensive article — titled “What is a War Crime?” — published in 2019 in the Yale Journal of International Law.  His observation is used there to support the article’s comment that “rules regulating the conduct of war are hardly new.”  Recounting the history of “war crimes,” the Yale scholars trace the legal codes that supposedly govern the conduct of war back at least to Deuteronomy in the Hebrew Bible, to Mahabharata, the ancient Indian epic tale of a Kurukshetra War, and even further back in time.

Those scholars found that the phrase “war crime” had apparently first appeared in print in an article in German in 1872, referring to that concept as kriegsverbrechen.

In America, the earliest formal attempt to punish crimes during war was the so-called “Lieber Code,” established by President Abraham Lincoln in 1863, directing the Union armies during the Civil War to avoid “all cruelty and bad faith concerning engagements concluded with the enemy,” and warning that violations “shall be severely punished.”

Today, though, the meaning of “war crime” is no more settled than it ever has been.  What, exactly, did President Biden mean this week when he said that evidence needs to be gathered to prosecute Russian President Vladimir Putin for war crimes during the ongoing Russian invasion of Ukraine?  Much of the world, it seems, is calling for prosecution of Putin for the “Bucha Massacre,” gruesome atrocities in a small suburb of Ukraine’s capital city, Kyiv.

Ukraine’s President Volodymyr Zelenskyy has said that what is now happening across his nation is “genocide,” the intentional extermination of all of a nation’s people.  That is commonly understood as a war crime, as are torture and the ill-defined “crimes against humanity” – the catch-all violation that led to the Nuremberg trials of former Nazi leaders before a military tribunal in Germany after World War II (a crime that never existed prior to Nuremberg, resulting in a still-lingering controversy over whether a war crime can come into being and be punished after the acts had already occurred).

“Nuremberg,” famous enough to be called to mind by a single name, was meant to be an orderly legal accounting rather than an act of primal revenge.  Its high aspirations were reflected in the opening remarks of its chief prosecutor, Robert H. Jackson (a U.S. Supreme Court Justice, on leave for that assignment).  Here are but a few of his soaring passages:

“That four great nations, flushed with victory and stung with injury, stay the hand of vengeance and voluntarily submit their captive enemies to the judgment of the law, is one of the most significant tributes that Power has ever paid to Reason….The common sense of mankind demands that the law shall not stop with the punishment of petty crimes by little people.  It must also reach men who possess themselves of great power and make deliberate and concerted use of it to set in motion evils which leave no home in the world untouched.”

Now, 77 years later, where would a prosecution for war crimes in Ukraine be carried out?

International law has established that every nation’s courts have the authority to enforce the law of nations (“universal jurisdiction”), on the theory that violations of those norms harm the entire international order.  The law of nations can be established by treaties among nations – like the famous Geneva Conventions of 1949 — or, simply, by accepted norms among willing countries.

Under the U.S. Constitution, according to long-standing Supreme Court precedent, treaties can only be enforced in American courts if Congress has passed a law to implement such an agreement.  War crimes, in fact, can be prosecuted in U.S. courts, under the War Crimes Act passed by Congress in 1996.  That Act criminalizes any act, inside this country or abroad, that amounts to a “grave breach” of the Geneva Conventions, without further definition.

For more than 20 years, the U.S. military has been operating war crimes tribunals at the U.S. naval station in Guantanamo Bay, Cuba, under a system first set up by President George W. Bush after the 9/11 attacks and then approved by Congress.  However, that system has encountered an almost endless variety of complications and frustrations, with few results.  The Supreme Court, aside from one major decision in 2008 allowing foreign nationals held at Guantanamo to go to federal court in Washington, D.C., to challenge their continued captivity, has refused to extend constitutional rights to those being prosecuted there.

The people of Ukraine might even attempt to sue Putin or Russian military and political leaders in U.S. courts for international law violations under the Alien Tort Claims Act, passed by the very first Congress in 1789 – a law that has had a vigorous revival in modern times as concern over international human rights abuses has grown.  However, the Supreme Court has recently been narrowing the scope of that Act, so that any human rights violations must have had some link to actions within this country.  Since a breach of the law of war is said to be universal in impact, would that suffice, at least in theory?

War crimes also can be prosecuted in the International Criminal Court, which sits in The Hague, Netherlands.  Indeed, that Court has already begun investigating the possibilities of prosecutions growing out of the invasion of Ukraine.  Forty-two nations, so far, have urged the ICC to pursue war crimes cases over human rights abuses against Russia’s neighbor and cultural kin.

That court has wide jurisdiction, claiming the authority to reach war crimes even in nations that are not formally parties to the treaty creating that tribunal.  There have been other specialized international crimes courts there, too, growing out of military conflicts in such places as Rwanda and Yugoslavia.

The ICC was created by the Rome Statute, a 1998 treaty – to which, it is important to note, the United States government has never become a party.  President Bill Clinton signed the treaty for the U.S. in 2000, but the pact has never been submitted to the Senate for ratification because the U.S. has always insisted – without success, to date – that the tribunal should not be empowered to reach actions by U.S. citizens committed within this country, based on the argument that the U.S. Constitution confers judicial power over the people here only on U.S. courts.

The ICC has long been a target of complaints, most vehemently in conservative political circles in this country.

The Obama and Biden Administrations continued to insist that the U.S. would not compromise its sovereignty by fully submitting to the ICC’s jurisdiction, but both of those Administrations pledged cooperation in ICC investigations aimed at other nations.  Former President Donald Trump, while in office, strenuously attacked the ICC, even revoking visas so that its prosecutors could not even enter this country.

Although war crimes prosecutions are hardly a new phenomenon, the efforts to enforce the international law of war changed significantly in the 20^th Century.  Before then, obligations to enforce treaties, including those regulating the conduct of war, were imposed on each nation as a sovereign member of a global community.  Each nation could be held accountable to another treaty partner for violating the norms.  Individuals were prosecuted under their own nation’s internal laws if those laws made it a crime to breach a law of war, as with Lincoln’s Lieber Code and the modern U.S. War Crimes Act of 1996.

After World War I, the victorious allied powers attempted to hold Germany’s Kaiser Wilhelm II personally liable for violating “international morality” under the Treaty of Versailles, but the Netherlands, to which he had fled, refused to give him up without a specific obligation in that treaty to obey the laws of war.  He was never prosecuted.

However, that changed with the Nuremberg trials after World War II, with Nazi leaders charged personally.  The allied powers in 1943 created the United Nations War Crimes Commission, expressly to investigate and prosecute criminal conduct by Germany’s wartime leaders.  The trials began November 1945, mere months after war’s end.

The International Military Tribunal created then declared that “crimes against international law are committed by men, not by abstract entities, and only by punishing individuals who commit such crimes can the provisions of international law be enforced.”

Controversy that arose during those trials, especially over retroactive prosecution for earlier conduct, continued for decades after.  It was not until 1993 that the next war crimes prosecution began, with a special tribunal for crimes in the former Yugoslavia.  For that prosecution, and later such proceedings, the charges were based on crimes that had been formulated previously, thus avoiding the flaw that haunts the memory of Nuremberg.

If violations of the law of war are found to have occurred during Russia’s war against Ukraine, a firm legal foundation has already been laid for prosecution, a foundation settled within the world community even if their specific meaning still remains a matter of profound debate.