I wonder if you could expand on this a bit? I have no idea what would happen, and your insights on other points cause me to want your views on this issue as well.
Either one of our troops will kill an illegal looking for a job, or some drug load scumbag will off one of our troops.
Putting a bunch of young high strung Marines and Soldiers on the border is a recipe for disaster.
Combat troops should not train or practice to be police officers. They are combat troops and should train as such and practice as such.
If troops are needed to augment the Border Patrol, them take the MP's, at least they have been through a law enforcement training academy and would understand the mission.