Last week I joined several of my colleagues in sending a letter to President Obama requesting clarification of his criteria for the lethal use of drones overseas. Administration officials assure us that a “high degree of confidence” is required that the person targeted by a drone is a terrorist. However, press reports have suggested that mere “patterns of behavior” and other vague criteria are actually being used to decide who to target in a drone strike. I am concerned that an already troublingly low threshold for execution on foreign soil may be even lower than we imagined.