[alkonaut]

An aerial bomb is equally indiscriminate. You make a judgement about the target value and the estimate collateral damage/civilian casualties and you fire if the equation is reasonable. Same here. If it's a muddy square kilometer of trenches do you KNOW there are no civilians? No. But it's not indiscriminate. The target area selection is the key. You can't release an indiscriminate autonomus killer drone into a city of course. But I doubt it'll be long before these drones make target distinction of humans (Vehicle recognition is old at this point).

Just like with land mines it's the military value vs risk of civilian casualties that determine if it's a war crime or not. Some countries have signed the Ottawa treaty, but notably not the US or Russia. And the trend isn't going towards states signing the treaty but rather towards leaving it.