Editor’s Note: This is Part I of a two-part series. The second article is available here

In 1942, three years before World War II came to a close, international lawyer Hersch Lauterpacht prepared a memorandum for the Committee on Crimes Against International Public Order. In it, he considered whether the Nazis should be tried for war crimes when the war ended. Before he could address when and whether to prosecute the Nazis for war crimes, he observed, it was first and foremost necessary to determine “what is a war crime.” Nearly 80 years later, this question looms yet again—this time in the horrific Syrian civil war.

No international court or tribunal currently has jurisdiction over the vast crimes committed in Syria since 2011. It seems unlikely at the moment that Syria itself will provide an accounting, and the prospect of the United Nations Security Council agreeing to establish a new tribunal or refer the Syria situation to the International Criminal Court (ICC) appears slim. As a result, domestic courts, mainly in Europe, have taken the lead in pursuing criminal accountability for crimes committed in Syria. The International, Impartial, and Independent Mechanism (IIM), established by the UN General Assembly in 2016, is also beginning to assist domestic Syria-related prosecutions.

As domestic courts outside of Syria begin to take on responsibility for prosecutions, it has become clear that there remains significant confusion over the proper scope of a war crime—that is, what, exactly, is a war crime, and how do we know? This matters because most domestic courts will exercise universal jurisdiction only over war crimes and crimes against humanity, or have statutes specific to “war crimes” prosecutions. As a result, some crimes may slip through the cracks if courts adopt an excessively narrow understanding of war crimes. Moreover, the legitimacy of the practice of prosecuting these international crimes domestically might be called into question if domestic courts define war crimes in wildly different ways.

We have recently written an article that addresses this question. In this post, we draw on that article to explain how overreliance on the concept of prior “criminalization” has caused disagreement about the proper scope of war crimes. We show that this overreliance may hinder domestic courts in addressing war crimes in Syria and elsewhere. (In a forthcoming post, we will put forward our own alternative approach to defining a war crime.)

History of the Problem: From Grave Breaches to “Criminalization”

The Nuremberg Tribunal famously declared that individuals could be held accountable directly for violations of the laws of war, as “[c]rimes against international law are committed by men, not by abstract entities.” But what was the reasoning exactly? The Tribunal offered an unsatisfying answer (even though, as documented in The Internationalists, it had good arguments before it): “[E]nough has been said,” the Tribunal concluded, “to show that individuals can be punished for violations of International Law.” The Nuremberg Tribunal’s cursory treatment of concerns about retroactivity opened the door to accusations that the tribunal had ignored the dictates of justice. The failure of the tribunal to fully and adequately justify individual liability—and the flood of criticism that followed—would lead future courts to over-correct by insisting on evidence of prior criminalization.

The 1949 Geneva Conventions codified the rules governing armed conflict, but did not define “war crimes” to which individual criminal liability would attach. Instead, Article 147 of the Conventions obligated state parties to enact legislation providing effective penal sanctions for persons committing “grave breaches” of the Conventions. In 1977, with the entry into force of Additional Protocol I to the Geneva Conventions (which the United States still has not ratified), it was made clear that such “grave breaches” “shall be regarded as war crimes.”

Today the statutes of several contemporary international criminal tribunals, including the Rome Statute establishing the International Criminal Court (ICC), provide jurisdiction over a variety of international humanitarian law (IHL) offenses termed “war crimes.” However, defining the full category of offenses that constitute war crimes but are not “grave breach” offenses remains an elusive task.

So what is the proper scope of “war crimes”? In an effort to answer this question, a number of courts and tribunals have looked to prior “criminalization” as a required element of a war crime. In Tadic, the ICTY’s first war crimes decision, for example, the Appeals Chamber famously found that in order for an offense to be subject to prosecution, “the violation of the [IHL] rule must entail, under customary or conventional law, the individual criminal responsibility of the person breaching the rule.” To establish this, the Tribunal cited “many elements of international practice” including multiple domestic military manuals, domestic statutes, two prosecutions of war crimes during the Nigerian Civil War, and two U.N. Security Council Resolutions concerning Somalia, stating that persons who breached IHL prohibitions would be held “individually responsible.” Other tribunals have looked to even more varied sources.

We argue that this approach to defining a “war crime”—relying on prior “criminalization”—is flawed. The need to prove that offenses have been previously “criminalized” has produced inconsistent results and uncertainty about the corpus of war crimes. Looking for prior criminalization to determine whether an act is a war crime also leads courts to engage in circular reasoning: an act is a crime only if a court, tribunal, or other governmental body has found that it is a crime. This has dire consequences for prosecutions of war crimes in domestic courts: when domestic courts and prosecutors are called to assess whether a particular act mentioned in a domestic statute amounts to an international “war crime,” the “criminalization” approach fails to provide clear guidance as to what, in fact, is a war crime.

The Current Challenge: Domestic Prosecutions of Syrian War Crimes

There are already efforts currently under way in several European states to prosecute perpetrators of war crimes in Syria. These prosecutions are often pursued by specialized prosecutorial authorities or war crimes units. In some cases, the crimes being charged are defined as international crimes, even though they are incorporated into domestic statutes or penal codes. There have been multiple successful convictions in Sweden and in Germany, with more cases underway. There are a small number of trials, and some other convictions, in other countries as well.

The problem with the prior “criminalization” approach for these cases is that it threatens to press domestic courts to look to international jurisprudence for pre-existing evidence of criminal liability. But that evidence is often not what it seems. The ICC, for instance, has treated the concept of “criminalization” as coextensive with the definition of war crimes in the Rome Statute. In Prosecutor v. Lubanga, the ICC’s first war crimes trial, the Pre-Trial Chamber rejected the Defense’s contention that Thomas Lubanga Dyilo, a military commander in the Democratic Republic of the Congo, did not have notice that the use of child soldiers constituted a war crime on the grounds that the Rome Statute included this offense explicitly.

That approach may make sense for the ICC, but it can create problems if domestic courts follow suit. Article 8 of the Rome Statute grants the ICC jurisdiction for “war crimes,” but it is “far from . . . a faithful snapshot” of all of the customary international war crimes. In the words of former ICTY Judge Abi-Saab, Article 8 is a “mere ‘artist’s sketch’” of the broader category of “war crimes” in general international law. Dapo Akande has recently voiced agreement, noting that the drafters of the Rome Statute specifically omitted from Article 8 a number of crimes that otherwise might qualify as “war crimes” under international law. If domestic courts treat the statute as a definitive guide to “war crimes”—even when their statutes permit otherwise—they may take an under-inclusive approach.

In a subsequent post, we will outline an alternative approach to defining a war crime that we argue avoids the shortcomings of the prior criminalization approach.

IMAGE: Assyrian Christians, who had fled the unrest in Syria and Iraq, attend a prayer for the 220 Assyrian Christians abducted by Islamic State group jihadists from villages in northeastern Syria February 2015. (Photo by ANWAR AMRO/AFP/Getty Images)