Defense Secretary Pete Hegseth's so-called Department of War threatened to court-martial Sen. Mark Kelly (D-AZ) after he appeared in a video stating that U.S. troops have a constitutional duty to refuse illegal orders.

"The Department of War has received serious allegations of misconduct against Captain Mark Kelly, USN (Ret.). In accordance with the Uniform Code of Military Justice, 10 U.S.C. § 688, 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 Department of Defense said in a statement on Monday.

"All servicemembers are reminded that they have a legal obligation under the UCMJ to obey lawful orders and that orders are presumed to be lawful," the statement added. "A servicemember's personal philosophy does not justify or excuse the disobedience of an otherwise lawful order."

President Donald Trump has suggested that the Democrats who reminded troops of their duty to refuse illegal orders could be hanged for treason.

"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," Kelly told CNN last week. "I think his reaction is just characteristic of a political system that no one is proud of right now."