President Donald Trump on Thursday called several Democratic veterans and national security specialists “traitors” who should face the death penalty for releasing a joint video where they said that U.S. service members could refuse illegal orders — a move that has prompted some lawmakers to call the president’s rhetoric “dangerous” and “a threat.”

“This is really bad, and Dangerous to our Country. Their words cannot be allowed to stand. SEDITIOUS BEHAVIOR FROM TRAITORS!!! LOCK THEM UP???,” Trump wrote on social media Thursday morning.