The probe comes just days after Senator Mark Kelly and five other Democratic lawmakers posted a video urging US service members to refuse illegal orders|Gage Skidmore|CC BY-SA 2.0

The Pentagon has opened an investigation into Arizona Senator Mark Kelly, saying it received “serious allegations of misconduct” against him.

The move is unusual because Kelly is a retired Navy captain and a vocal critic of the Trump administration’s military actions.

The probe comes just days after Kelly and five other Democratic lawmakers posted a video urging US service members to refuse illegal orders.

They questioned whether recent Pentagon strikes on suspected drug smugglers in Latin America violate the laws of war. President Trump harshly condemned the video, calling the group the ‘Seditious Six’.

Defense Secretary Pete Hegseth blasted the video, calling it confusing and dangerous to troops. He said Kelly is the only one being investigated because he remains under the military justice system as a retired officer who can be called back to duty.