In his appearance with Secretary Clinton at NBC’s Commander-in-Chief Forum earlier this month, Donald Trump called for actions that amount to a war crime. Addressing US policies in the Iraq war, he said, “You know, it used to be to the victor belong the spoils… I always said: Take the oil.” This was no slip of the tongue. Mr. Trump said the same in his August national security speech, and in his recently revised book. In reaction to Trump’s statements at the NBC Forum, former New York Mayor Rudi Giuliani claimed that “until the war is over, anything is legal.” There may be no need to stress to this audience that neither of these statements comports with the laws of armed conflict, but the fact that they would risk criminal liability for US personnel if carried out warrants greater discussion.

In response to Giuliani’s comments about Iraqi oil, ABC’s George Stephanopoulos asked “wouldn’t that just be theft?” Not quite. It would actually be pillage, which means theft during war. Pillage is a modern war crime with a solid grounding in the history of international criminal law, including as a sanction for the illegal exploitation of oil from war zones. At present, the International Criminal Court (ICC) is prosecuting two senior politicians for pillaging different types of property. The crime is a staple of most international tribunals. And several national courts are also trying the war crime. Presidential candidates, their supporters, and all those men and women operating in modern resource wars would be well advised to learn something of this war crime’s history.

On this score, Trump is correct about one thing: it’s true that “it used to be to the victor belong the spoils.” Still, this was true over two hundred years ago, and much has occurred in the intervening period to change that reality. Most notably, States decided to criminalize pillage in armed conflicts. Several centuries ago, the laws of war incrementally prohibited pillage during war, first by restricting it to situations where a local population refused to surrender, necessitating a siege, then prohibiting the practice categorically so that even this exception was outlawed. These steps came about partly because permitting the practice undermined discipline among the military but also because it created perverse incentives for going to war in the first place. This venerable history is reflected in the archaic language at least one modern definition of pillage still includes. The ICC Statute prohibits “Pillaging a town or place, even when taken by assault.” The key term—pillage—is all that matters legally. 

The American experience of war played a crucial role in bringing about this prohibition. By the time Abraham Lincoln commissioned Francis Lieber to draft a code of laws applicable to the American Civil War, pillage was firmly established as a criminal prohibition in wartime. Lieber, who had sons on both sides of the Civil War, included a provision in the now famous Lieber Code of 1863 that categorically prohibited “all pillage.” Since then, all codifications of war crimes have included pillage, from the list drawn up by the Allies post-World War I to the US War Crimes Act, which first entered into force in 1996. The risk this war crime creates for militaries, their advisors, politicians and businesspeople involved in resource exploitation during wartime requires far greater consideration.

To cite one example, Mr. Trump’s repeated statements that the US should “take the oil” find a chilling legal parallel at Nuremberg, where the offense of pillage was used to punish Nazis for their theft of natural resources, including oil, from throughout occupied Europe. In one instance, the Nuremberg Tribunal convicted Walther Funk, the Reich Minister for Economic Affairs and President of the Continental Oil Company, of pillaging oil seized from locations in Eastern Europe. According to Funk’s own testimony, whenever German troops seized oil wells, German officials assigned the Continental Oil Company the task “of producing oil in these territories and of restoring the destroyed oil-producing districts.” American forces can prevent oil falling into ISIL’s hands in Iraq and the laws of war do allow a very limited humanitarian exception to the basic prohibition, but they don’t permit a foreign force to “take the oil” as their “spoils” and certainly not on the assumption that they’re operating in a law-free zone.

There are also several contemporary developments that increase the risk of liability for pillaging natural resources. Most recently, the Office of the Prosecutor at the International Criminal Court published a new policy earlier this month raising the priority that institution will give to this offense: “The Office will give particular consideration to prosecuting Rome Statute crimes that are committed by means of, or that result in, inter alia, the destruction of the environment, the illegal exploitation of natural resources or the illegal dispossession of land.” (Emphasis added.) Only a few years ago, the Dutch and Canadian governments jointly sponsored a major event at the Peace Palace in The Hague to launch new research on the ways pillage applies to the illegal exploitation of natural resources in contemporary warfare. Since then, Swiss authorities have opened a formal investigation into one of the largest gold refineries in the world, and a Belgian businessman is currently awaiting trial in Brussels for allegedly collaborating with former Liberian President Charles Taylor and a rebel group in pillaging diamonds from Sierra Leone.

Most importantly, the US War Crimes Act also gives US federal courts jurisdiction over pillage, even when the crime was carried out in foreign theatres of war. True, to date this Statute has proved more symbolic than effective, but it should give pause to those who might be tempted to “take the oil” from Iraq or elsewhere. Such an official policy would create risks for American servicemen and women called to implement the orders, not to mention the political and military leaders themselves and the businesspeople with whom they collaborate. Indeed, US military officials would be under an obligation to refuse such manifestly illegal orders. What is more, as various German nonagenarians are discovering first hand these days, transgressing these laws risks liabilities at home that can endure for a lifetime. The trials of these very elderly German defendants also show that what is politically unthinkable presently may not be in fifty years from now, reinforcing the need to take pillage ever more seriously today.

Even if Mr. Trump never assumes the Presidency or does but never adopts a policy to follow through on his words about Iraqi oil, the call for actions that amount to a war crime is troubling. One of the reasons for the great interest in pillage’s application to illicit resource transactions is its ability to disincentivize wars by predatory nations bent on stealing natural resources from foreign countries. Ironically, the United States went to war in Iraq in 1991 as part of Operation Desert Storm to confront precisely this problem, when Iraq invaded Kuwait for oil. So, quite apart from creating risks of serious criminal responsibility for US politicians, servicemen, servicewomen and businesspeople, Trump’s advice denigrates the reasons for sending troops into harms way in Iraq, and places America in very poor company politically. Beyond Iraq, this policy would also set a disastrous precedent other states could well emulate, further undermining global security. Legally and politically, then, “taking the oil” is not in the United States or any other peace-loving nation’s best interests.