A landmine is not an autonomous weapon. Autonomy suggests being able to select a target and harm only that target. A landmine just blows up when someone steps on it; there is no selection, thus no autonomy.

A landmine is programmed to attack a target of a specific weight when it enters a specific area. The targeting model was programmed by engineers to try and target soldiers (or armoured vehicles), and the locations they were placed were also for that purpose. However, it's possible for the heuristics to fail, and for a mine to blow up a child, because the weights weren't tuned correctly, or to fail to explode when a soldier steps on it.

By your same logic, any AI has no autonomy, because it does X when its code selects X. A guard dog robot attacks will act consistently given identical inputs.

> A landmine is programmed to attack a target of a specific weight when it enters a specific area.

You've literally just said it is programmed. If it is programmed, how can it be autonomous?

Because it kills without consulting the people who put it there.

AI is also programmed; it attacks when the score returned by the threat function exceeds a threshold.

Unless we're talking about AGI, in which case I misunderstood and assumed we were talking about AI that we can currently make.