If the “no-go” lines are clearly marked, I do not have a problem with this system.
The trouble with this rational statement is that we'd all be surprised at what the enemy and their brainless supporters would deem "clearly."
Personally I would add that anyone with their facial features hidden, within the safety zone and carrying obvious weapons or containers of anything are targeted and shot on the spot, no questioned asked.
I have to resort to the obvious observation about war. There can be no rational basis for any "obligation" on the part of the victim of infiltration, for reciprocity in the number of casualties, nor for so-called "proportional response."