Dear POTUS,
No doubt you wish the mass expulsion of illegal aliens to be one of the positive aspects of your legacy. This is not about the politics of that goal.
The police, guard and marines personnel share the desire to serve. It takes better than average people to serve well. But they, like most of us, are not mental giants. The capability to make split-second decisions is enhanced by their training, specialized to the scenarios they are expected to encounter.
A policeman is not trained to storm an objective requiring lethal force from the get-go. The training of a cop involves a very careful sequence of escalation: request, demand, compel. Execution of this template, switching almost instantaneously to deadly force according to the regulations of a department, is the hallmark of superior training and ability. The ability to persuade a suspect to comply with minimum force, or any force at all, is far more complex than the use of deadly force. This is what makes the career of law enforcement rewarding. It maintains the consent of the governed, without which civil government loses all meaning. A cop practices his skills every day.
The training of the national guard in police work is occasional and rarely practiced. The Guard is not a law enforcement agency. Training for civil unrest is combined with the training of a combat infantryman, which is almost entirely occupied with perfection in the use of lethal force. This combination leads to the possibility of horrendous error, when a unit of guardsmen spontaneously switches from civil policing to the massive application of lethal force.
The U.S. Marines train hard to kill. “No Better Friend, No Worse Enemy” is a valiant motto, full of honest intent. But the potential risk of misidentification of a civilian as an enemy combatant, and the resulting application of lethal force, remains. It is impossible to guarantee that a Marine in a civil situation will suppress reflexes developed for combat.
History is replete with unfortunate examples:
William Calley was by all accounts a decent guy, who regretted the My Lai massacre for the rest of his life.
The Kent State shootings were committed by 28 frightened guardsmen.
The 2005 Haditha massacre in Iraq was committed by Marines enraged by a lethal IED. While the participants have been partly excused by the character of the war zone, a domestic response would be unforgiving.
The risk exists of unintended death of of civilians, in confrontation with soldiers lacking the trained finesse of professional police officers. The event is not a desirable legacy.. It makes political sense to avoid fatalities committed by federal forces. The best way to avoid this is to use the Guard and Marines strictly in a defensive capacity. Powers of arrest and detention should remain the province of DHS and other federal agencies with experience in law enforcement.