The United Nations spends a lot of time considering things that could be used against humans during times of war. One of the things that the UN has been considering recently are the use of automated robots with weapon systems on the battlefield. The UN is strongly against any use of autonomous robots with the ability to end human life.
While many of us immediately think of science fiction when it comes to robots with the ability to kill humans with no input from a human operator, we're not talking about far-fetched Terminator style robots. What the UN is worried about are automomous robots such as aerial drones able to identify targets and launch missiles or drop bombs with no human interaction.
The UN is also concerned about weapons such as small mobile robots using tank-like treads that are equipped with guns and other weapons systems that can roll through an environment engaging targets on their own volition. It is worth noting that most of these weapon systems are available, but they are typically controlled by a human operator from afar.
The UN recently issued a 22 page report talking about lethal autonomous robotics or LARs weapon systems. The UN wants member states to work to articulate a policy for the international community that would ban robots and robotic systems from being able to take human life without human intervention. The human report says, "[LARs] deployment may be unacceptable because no adequate system of legal accountability can be devised, and because robots should not have the power of life and death over human beings."