I'm a British veteran and from the first day if basic training your are told over and over and over not to follow an illegal order, honestly sending in the marines would prob be better for the public than the pigs troops are from shit holes and just needed the money most of the yanks I worked with would never fire on protesters.
But you know I might be wrong.
Honestly mate I don't think the armed forces would exist for very long if he gave that order, most troops would change teams on the spot.