There is growing concern in some quarters that the drones used by the United States and others represent precursors to the further automation of military force through the use of lethal autonomous weapon systems (LAWS). These weapons, though they do not generally exist today, have already been the subject of multiple discussions at the United Nations. Do autonomous weapons raise unique ethical questions for warfare, with implications for just war theory? This essay describes and assesses the ongoing debate, focusing on the ethical implications of whether autonomous weapons can operate effectively, whether human accountability and responsibility for autonomous weapon systems are possible, and whether delegating life and death decisions to machines inherently undermines human dignity. The concept of LAWS is extremely broad and this essay considers LAWS in three categories: munition, platforms, and operational systems.