Killing machines

Not content with controlling drones from Nevada to kill people in Iraq and Afghanistan, the US is now researching the use of robots instead of men on the front line. One scientist involved in this project said it was very difficult to progamme robots to have a moral code. One solution to prevent them from killing civilians by mistake is to input some instruction like, "if in military uniform, kill; if in civilian clothes, do not kill" but this is clearly inadequate when dealing with insurgents.
I was thinking that such killing machines could be put to good use when dealing with pirates attacking oil tankers. They could be lined up around the tanker and programmed to shoot any person attempting to board the vessel while it is in motion.