The UK's policy on this issue is clear: it must be in line with applicable UK and international law, and bound by UK rules of engagement, targeting and operational directives. The same laws are adhered to whether the method used is an unmanned and remotely piloted air system (also referred to as drones), a piloted aircraft, or any other weapon.
Under international law, the UK has an inherent right to self-defence against both armed attacks and imminent threats of armed attack. Where a direct and imminent threat to the UK is identified, and there is no other effective option, the Government reserves the right to take lawful action in self-defence to address the identified, imminent threat to the UK and/or UK interests and to report to Parliament after it has done so. This has my full support. The duty of the Government is to protect the population at home from attack whether from terrorists returning home or from more conventional forces.
The UK also expects others to follow the same international laws when it comes to the use of military force. This applies to the use of armed drones, as to any other weapon, including when used against terrorist targets.
One purpose of the Ministry of Defence's Joint Doctrine Publication on Unmanned Aircraft Systems (UAS) is to increase transparency and understanding around the use of military drones. The doctrine applies to all uses of UAS across Defence at the operational level and it guides operational commanders and planning staff in understanding the terminology, tasking and employment of military drones.