ROE are not stagnant, rules can change if the situation necessitates.
“Troops will not be allowed to detain immigrants, seize drugs from smugglers or have any direct involvement in stopping the migrant caravan...”
Troops can’t engage them, but their equipment (barriers, concertina, etc.) can spot & block them.
As long as they can defend themselves without going up the chain of command to the Pentagon, I’m cool........... for now.
BTW, glad this is a USMC operation. Semper fi, do or die, Hoorah.