Members of the U.S. military have the legal right to refuse orders they believe are unlawful, but they risk violating military laws of obedience if the order is in fact lawful, experts in military law say.

Service members are expected to presume their orders are lawful — if they relate to military duty and comes from a proper authority in the chain of command — unless the orders fit into a “small subset” of egregious orders that would constitute war crimes. That standard was set in the Nuremberg trials after World War II, in which Nazis could not defend their crimes as simply obeying orders.

Most orders that blur the line between lawful and unlawful, however, reside in a gray zone in which soldiers, airmen, sailors, Marines and and coast guardians are not obliged to disobey. It is in their right to refuse an order, but — by the time the order has reached them — a military lawyer has likely already made a judgment about the legality of the order, former armed services lawyers told ABC News.

Military orders have come under the microscope in Washington in recent days after a group of Democratic lawmakers — all of whom are military veterans or served in the U.S. intelligence community — posted a video in which they told members of the military their oath of enlistment calls for them to refuse “illegal orders.”

“Right now, the threats to our Constitution aren’t just coming from abroad, but from right here at home,” the lawmakers told service members. “Our laws are clear: You can refuse illegal order. … You must refuse illegal orders. No one has to carry out orders that violate the law or our Constitution.”

Sen. Mark Kelly, an Arizona Democrat who served 25 years in the Navy and as a NASA astronaut, said the group was simply “standing up for the Constitution.”

“I think it’s important to say that there is nothing more American than standing up for the Constitution, that’s what we were doing. President didn’t like it, so now he calls for us to be hanged,” Kelly told CNN.

Sen. Elissa Slotkin, a former CIA officer who participated in the video, told ABC News’ “This Week” on Sunday that the lawmakers put out the video because they had been approached directly by military officers with concerns.

“We’ve had report after report of legal officers, JAG officers, coming forward and saying, ‘Look, I push back on this. I’m not sure that this is legal,'” Slotkin said. “There is such things as illegal orders. That’s why it’s in the Uniform Code of Military Justice. Going back to Nuremberg, right? And it’s just a — it’s a totally benign statement.”

According to retired Lt. Col. Rachel VanLandingham, a professor at Southwestern Law School and a former judge advocate general (JAG) in the U.S. Air Force, a service member “must” refuse orders only in the cases of “patently” unlawful actions, in keeping with the Nuremberg principle.

In a press release Monday, the Department of Defense said it would open an investigation into Kelly for his participation in the video.

Military law, known as the Uniformed Code of Military Justice, applies to military retirees, a status attained after 20 years of service which confers a pension tied to rank.

Defense Secretary Pete Hegseth, echoing President Donald Trump, labeled the video “seditious.”

“Encouraging our warriors to ignore the orders of their Commanders undermines every aspect of ‘good order and discipline,'” Hegseth wrote on X Monday.

The Pentagon “is reviewing his statements and actions, which were addressed directly to all troops while explicitly using his rank and service affiliation — lending the appearance of authority to his words,” he added.

Vice President JD Vance also weighed in on social media: “If the president hasn’t issued illegal orders,” he wrote, “[then] members of Congress telling the military to defy the president is by definition illegal.”

John Dehn, a professor at the School of Law at Loyola University of Chicago and a former Army JAG officer, said the administration could contend the video raises questions over the separation of powers.

“I think what the Vice President is trying to say is that members of Congress should not be prejudging the legality of orders that might be issued, and that doing so has a tendency to interfere with the military chain command,” Dehn said.

Yet it “is not resolved” whether the statute referenced by the Pentagon — which deals with an “intent to interfere” with military loyalty and morale — could be used to prosecute “members of Congress reminding service members of their basic obligation not to carry out unlawful orders,” he added.

For service members, choosing to disobey is a risk.

“The risk is on the service member if they choose to disobey an order and that order turns out to be lawful,” Dehn said. “They assume the risk that it may be lawful when they disobey, which is another reason why, when soldiers ask about this, we advise them to seek clarification, and legal advice if possible.”

“Disobedience isn’t the first step,” he said.

A military judge — and not a jury — would render a determination on whether an order disobeyed was lawful, experts said.

“The law cloaks all orders on the presumption of legality, as long as it’s given by a proper authority and and related to a military duty,” VanLandingham said. “The default is that you follow all orders, and all orders are presumed lawful.”

That default is “understandable,” VanLandingham said, “because the military for centuries has been a hierarchical organization whose lifeblood, whose main dynamic, is obedience to orders.”

“My primary complaint about the video from the congressmen and women was that it failed to appreciate the quandary that service members are actually in,” VanLandingham added. “Strong obedience to orders are the defaul. … especially when you have things like lawyers telling you it’s lawful.”

In interviews in recent days, lawmakers in the video have called into question U.S. military action in the Caribbean Sea and Eastern Pacific Ocean against alleged drug smugglers — where 21 strikes have killed 83 people, according to the Defense Department — and federal deployments of the National Guard to U.S. cities like Los Angeles.

The lawmakers did not make those references in the video. Since it was published, Kelly and Sen. Elissa Slotkin, a former CIA officer who participated in the video, have said they can’t point to a specific recent military order they believe is unlawful, though Slotkin told ABC News’ “This Week” on Sunday that “certainly there are some legal gymnastics that are going on with these Caribbean strikes and everything related to Venezuela.”

It is not clear whether any service members have been asked to break the law.

VanLandingham says service members have been given “legal cover” from lawyers who have rendered judgments on lawfulness.

In the case of strikes as a part of the military’s counter-narcotics campaign, a classified memo from the Office of Legal Counsel at the Department of Justice, which was briefed to members of Congress, makes it exceedingly difficult for service members to refuse orders.

Service members can seek out a judge advocate, or military lawyer, if they feel uncomfortable with an order.

“You would access a military lawyer to ask for their advice on whether or not it’s lawful or not, and if you still think it’s unlawful, then you disobey it and you see what happens,” VanLandingham said.

“Service members disobey at their peril,” she said.

Hegseth has publicly disparaged military lawyers in recounting his experience with JAGs during his Army service. In February, the secretary fired the top-ranking JAGs for the Air Force and the Army.