MicroChip ‘em!! YES
Why not?
Micro Chip ...
I got one better. Micro explosive him ... drop him back in Mexico ... triggered the next time he crosses the border ... problem solved.
Too easy to remove and it is not obvious.
Do what they used to do in colonial America to criminals who they mercifully didn't hang. They branded them on the cheeks with a letter representing the crime they committed. Then they cropped their ears so the person was readily "recognizable" when out in public.
How about a nice big "IA" in one inch letters for illegal alien?
This one calls for a macro chip, one manufactured by Remington.