In a detailed scientific article just published online, physicist and peace researcher Jürgen Altmann (TU Dortmund, Germany) explains that armed uninhabited vehicles (on land, on/under water, in the air) do not exist in a legal vacuum.
For example, they must not be equipped with biological or chemical weapons. In Europe most land and air vehicles are covered by the definitions of the Treaty on Conventional Armed Forces (CFE Treaty), thus they are limited by numbers and subject to verification. If armed uninhabited vehicles cannot be prohibited outright, then limitations similar to the CFE Treaty are needed in other regions of the world. To avoid dangers for international humanitarian law and military stability, autonomous attack, that is attacks without a human decision in each single case, should be prohibited. Additional prohibitions are needed, among others, for small and very small armed vehicles.
Jürgen Altmann, Arms control for armed uninhabited vehicles: an ethical issue, Ethics and Information Technology, 2013, DOI 10.1007/s10676-013-9314-5. Read the full article (open access, 17 pages) here.