Drone strikes have become a key feature of counterterrorism operations in an increasing number of countries. This work explores the different domestic and international legal regimes that govern the manufacture, transfer, and use of armed drones. Chapters assess the legality of armed drones under jus ad bellum, the law of armed conflict, the law of law enforcement, international human rights law, international criminal law and domestic civil and criminal law. The book also discusses the application of law to fully autonomous weapons systems where computer algorithms decide who or what to target and when to fire.