Senator Mark Kelly could be recalled into active military service to face a court martial, the Defense Department said Monday, after investigating the Arizona Democrat and retired Navy officer for a video he and other Democratic lawmakers shared last week urging servicemembers to ignore illegal orders. 

Mr. Kelly and five other Democrats — one of whom is a retired CIA officer and four of whom are ex-military — shared their video last week amid concerns about the legality of military strikes in the Caribbean and possible troop deployments on American soil. 

Mr. Kelly accused the Trump administration of “pitting our uniformed military” against American citizens. The video did not explicitly mention any particular issue, but rather put out a general reminder that the military can and should defy an illegal order. 

On Monday, after the president spent the weekend raging against the six Democrats for behavior he called “seditious,” the Pentagon announced Mr. Kelly was being investigated.

“In accordance with the Uniform Code of Military Justice … and other applicable regulations, a thorough review of these allegations has been initiated to determine further actions, which may include recall to active duty for court-martial proceedings or administrative measures,” the Defense Department announced Monday. “This matter will be handled in compliance with military law.”

In its announcement, the Department of Defense explicitly cited a section of the United States Code that prohibits individuals from interfering with the “loyalty, morale, or discipline” of the military. Violations of that law carry a penalty of up to 10 years in prison. 

Defense Secretary Pete Hegseth called the lawmakers in the video the “Seditious Six” in a post on X on Monday. 

“The video made by the ‘Seditious Six’ was despicable, reckless, and false. Encouraging our warriors to ignore the orders of their Commanders undermines every aspect of ‘good order and discipline,’” Mr. Hegseth wrote. “Their foolish screed sows doubt and confusion.”

However, Mr. Hegseth said that only Mr. Kelly is under investigation because the others are not subject to the review being conducted. One is a retired intelligence agent and the other four are no longer subject to the Uniform Code of Military Justice.

Mr. Hegseth says Mr. Kelly’s words were especially harmful because they were “addressed directly to all troops while explicitly using his rank and service affiliation.”

“Kelly’s conduct brings discredit upon the armed forces and will be addressed appropriately,” Mr. Hegseth wrote. 

Mr. Kelly said that he first learned about the investigation from Mr. Hegseth’s post on social media. 

“If this is meant to intimidate me and other members of Congress from doing our jobs and holding this administration accountable, it won’t work,” the Arizona senator said in a post on X on Monday. “I’ve given too much to this country to be silenced by bullies who care more about their own power than protecting the Constitution.”

Observers like the former congressman, Justin Amash, noted that the investigation is likely to go nowhere since “We don’t live in North Korea.”

“The chances of a successful prosecution here are zero point zero percent. Everything with this administration is performative nonsense to cater to an ever-shrinking base,” Mr. Amash, who is a constitutional lawyer, posted on X. “Anyone here can freely state that service members must refuse unlawful orders.”