What I mean is, if your goal is to keep people out of a certain area, period, the drone will say "can do", and it will be able to do it with frightening precision and no doubts. Humans have natural stopping points.
One maybe stupid example is when there were lots of Syrian refugees on the way through Europe in 2015. We learned the hard way that, if people are pushing against your borders, the only way to keep them out is to eventually use force. We were not willing to do so, so we had to accept that and grant people asylum (which I think was the right decision).
Imagine (a bit scifi but for the sake of argument) "border patrol 2000", which will give a warning, then give a more stern warning, then raise a wall, then try rubber bullets, then try to keep you from climbing the wall with a grappling arm, and finally using live rounds. If you are really determined it will eventually have to shoot. Human solderies did shoot in the past but they did also sometimes not shoot, and it always had a political aftermath. But with automatic systems, it is too easy to psychologically detach, and to say it's e.g. the refugees own fault.