Human beings have been extremely easy to kill for our entire existence. No system of laws can possibly keep you alive if your neighbors are willing to kill you, and nothing can make them actually unable to kill you. Your neighbor could walk over and put a blade in your jugular, you're dead. They could drive into you at 15MPH with their car, you're dead. They could set your house on fire while you're asleep, you're dead.

The only thing which keeps you alive is the unwillingness of your neighbors and those who surround you to kill you. The law might punish them afterward, but extensive research has shown that it provides no disuasion to people who are actually willing to kill someone.

A military AI being used to wipe out large numbers of people is exactly as 'inevitable' as the weapons we already have being used to wipe out large numbers of people. The exact same people will be making the decisions and setting the goals. In that scenario, the AI is nothing but a fancy new gun, and I don't see any reason to think it would be used differently in most cases. With drones we have seen the CIA, a civilian intelligence agency, waging war on other nations without any legal basis, but that's primarily a political issue and the fact that it can be done in pure cowardice, without risking the life of those pulling the trigger, which I think is a distinct problem from AI.