Long were there rumors of "electric-eye powered" autonomous guns along the Berlin Wall - turns out they were just mines.

We culturally understood the problems here decades before we techologically understood the problems here. An autonomous weapons platform is going to need a few things: (1) territory (2) engagement protocol (3) disengagement protocol. (1) is easy. Geofence it and be done. (2) is gonna be tricky because unless you have triangulation, LIDAR or some other form of non-optical rangefinding, restricting engagement to the territory becomes error-prone. And that's if you instruct it to kill everything that moves. Is that ISIS-K poking a head over that rock? Or a pigeon? Okay you shot it and it stopped moving - is it dead? Or just playing dead? You should probably call over a Reaper just to take a peek and give human eyes on it at which point why didn't you just stick with the Reaper in the first place?

So... what do you do with a walking killbot, exactly? We have a hard enough time when our remote killing is done by the whole of the CIA chain of command. You're gonna give it over to a Roomba?