The threat of autonomous killer robots is very real and we have to stop them before it's too late. Such is the theme of many a sci-fi film, but it’s now also the official position of Human Rights Watch, which today published a 50-page report titled “Losing Humanity” that calls for an international treaty banning fully autonomous weapons technology from the battlefield. That makes perfect sense, though HRW is taking a rather straightforward stance toward technology and terminology that is anything but. Defining autonomy and just how autonomous is “fully autonomous” makes this a difficult issue to talk about in regulatory terms, much less to ban outright under internationally recognized rules of war.