Landmines are the OG killer robots, and the international ban on those has been pretty darn successful.

There's very few countries that haven't signed on (~five of the usual suspects) and even those holdouts appear to be fairly successfully deterred from using them because of the international disgust and outrage that it brings

Edit: Remember "don't let perfect be the enemy of good!" I see comments implying that because positive action isn't perfect it's pointless. That's not how progress is made