The issue originally surged to the forefront last year when the Trump administration repeatedly struck boats in the Caribbean officials alleged were carrying illegal drugs. Democratic lawmakers with backgrounds in the military and intelligence community then published a video reminding troops they “can” and “must refuse illegal orders.”

“No one has to carry out orders that violate the law or our Constitution. We know this is hard and that it’s a difficult time to be a public servant,” they said. “But whether you’re serving in the CIA, in the Army, or Navy, or the Air Force, your vigilance is critical.”

The issue of legal versus illegal military orders surfaced again this week when Trump escalated his threats against Iran, leading to bipartisan condemnation from members of Congress before he gave that country’s leaders two more weeks to negotiate.

But what exactly violates international law or rises to the level of a war crime is often murky, as is who would be willing to prosecute U.S. troops, according to experts interviewed by States Newsroom. 

Rachel E. VanLandingham, professor of law at Southwestern Law School in Los Angeles and a former judge advocate in the U.S. Air Force, said that “at the end of the day, the law of war does allow for a great deal of violence and a great deal of civilian suffering.” 

But several of the threats Trump has made, including to destroy power plants and bridges in Iran, would likely violate the law if the military were to carry them out, she said. 

“Under no stretch of interpretation would that be lawful, right? Because that just fails to distinguish whatsoever the civilian objects versus lawful military objectives, even if we stretch the definition of what's a lawful military objective,” VanLandingham said. 

The boat strikes in the Caribbean, including the decision to order a second strike on two survivors, could also have been illegal, she said. 

VanLandingham doesn’t expect the Trump administration will hold anyone accountable for actions the military has already taken or may take. But she noted there is no statute of limitations on the charges that would likely apply under the Uniform Code of Military Justice for military members or the War Crimes Act for anyone not subject to the military justice system.

“The next administration could come in and investigate our service members for alleged war crimes. And they should, to demonstrate renewed fidelity to U.S. law, to the law of war,” she said. 

Congress doesn’t have the authority to prosecute anyone for violating the law, but could hold oversight hearings with Defense Department officials, a scenario that would become more likely if one or both chambers return to Democratic control following the November midterm elections. 

“They can have public, open hearings and drag in every single military member that was involved in the chain of command of orders for striking Iran, if they wanted to,” VanLandingham. “That's not a criminal prosecution, but it's transparency.”

Lawmakers could also provide more funding and require the Pentagon to reinstitute the Civilian Harm Mitigation Program, which she said “the Trump administration has gutted.”

Geneva Conventions

Leila Sadat, the James Carr Professor of International Criminal Law at WashU Law School in St. Louis, Missouri, said that in a situation where the president directs the military to violate the laws of war, it’s highly unlikely military commanders or the Department of Justice would then turn around and prosecute those actions. 

Even if a prosecutor were to try, Trump would likely be insulated from any domestic prosecution for “official acts.” And as president he could issue preemptive pardons for any military members he believes could face future prosecution, either in the military or civilian justice system.

Trump has a history of absolving military members accused of violating military law, including in 2019, when he pardoned two officers in the Army for actions in Afghanistan and restored the rank of a Navy Seal who had been demoted for his conduct in Iraq. Trump later pardoned four contractors for killing more than a dozen Iraqi civilians in 2007.

But those protections only apply within the United States. 

The Geneva Conventions’ provision on universal jurisdiction would apply internationally and any country could choose to prosecute. 

“Now you still have to catch them, you have to get the evidence, but every state in the world is a party to the Geneva Conventions,” Sadat said. “So committing violations of the Geneva Conventions by attacking civilian objects, by attacking marketplaces, or hospitals, or schools, or electrical infrastructure, those kind of crimes can be prosecuted by every country in the world. So people should think about it before they do it.”

France, Germany, and Sweden have all used the principle of universal jurisdiction to prosecute Syrians for crimes they committed during the war in their home country, she said. 

“The one debate is, do you have to have the person on your territory before you can go forward? Or can you do an investigation even if the person is not on your territory?” Sadat said. “And many have argued that you can do the investigation even if the individual is not on your territory. Different countries have different rules on whether they accept trials in absentia.”

Sadat said that gets a bit more complicated when the Status of Forces Agreements that give the U.S. jurisdiction over alleged wrongdoing by U.S. troops in dozens of countries come into play. 

Sadat, who was a special adviser on Crimes Against Humanity to the International Criminal Court Prosecutor from 2012 through 2021, said if the U.S. military were to carry out some or all of the threats Trump posted to social media, that could have led countries to reconsider those agreements. 

"It could create a huge security problem for the United States eventually. And that's why I hope calmer heads are prevailing. Saying, 'You know, there's an entire complex web of treaties and agreements,'" she said. 

Trump would also likely pressure countries not to try U.S. military members for violating international law, but he may not always be successful, she said.  

"Eventually there's going to be a country in which that's not going to work,” Sadat said. “And so that's why you really do have to think of this a little bit differently, because there are external forces and external actors that could decide we're going to enforce the law, even if the United States is not going to enforce the law.”

Investigating US forces

Susana Sacouto, director of the War Crimes Research Office at American University’s Washington College of Law, said the Geneva Conventions require the U.S. to “investigate and … deal with alleged violations of the law of war by its own forces.”

How well that works in practice has “varied over time,” she said. 

"The problem is, we have an architecture, but those cases, particularly the criminal cases, are really exceptional, and they're really exceptional, especially regarding senior officials," Sacouto said. "So there's been a lot of criticism about whether that architecture that exists is actually functioning to routinely investigate our own military actions for potential war crimes or (international humanitarian law) violations." 

There is the possibility a future presidential administration may have defense officials or the Department of Justice look into allegations that emerge during the Trump administration. But Sacouto said, “past history with respect to accountability for U.S. officials, especially senior officials, is not very encouraging.”

Congressional investigations into the Central Intelligence Agency’s use of torture in the aftermath of the 9/11 terrorist attacks is one example Sacouto pointed to of a long-term investigation that did not lead to any high-level prosecutions. 

“Even then, no senior officials were really ultimately held accountable for their role in that program,” she said. “There were lower-level Abu Ghraib prosecutions, but no senior-level folks were found accountable.”