Dr. Nils Melzer, Study on the Human Rights Implications of the Usage of Drones and Unmanned Robots in Warfare (European Parliament Directorate-General for External Policies (DROI)) (May 2013) (full-text).
This study found that "[f]or the foreseeable future . . . any application of military force through armed drones must necessarily remain under the control of a human operator." It recommends that the European Union launch an intergovernmental consensus-building process including experts meetings on "legal constraints and/or ethical reservations."