Recent developments in the technology of unmanned aerial vehicles (UAVs) (drones) have opened up important new possibilities in the field of remote sensing. The development of appropriate national legislation has struggled to keep up with these developments. The state of development of this legislation in a number of countries is considered. An important distinction has to be made between the flying of UAVs as a hobby and flying them for commercial work (for present purposes commercial work is defined as commercial/industrial work, scientific research, environmental monitoring, crime detection, etc., in fact any purpose other than just for fun). Rules apply to the flying of a UAV for any purpose whatsoever, even as a hobby. It is becoming increasingly recognized that the pilot of any UAV is responsible for any accident, damage or injury caused by that UAV. More and more countries are requiring that anyone flying a UAV for commercial purposes must have satisfactorily completed a training programme before flying their UAV, and must comply with the relevant rules and keep a log of all flights. There is a problem that there have recently been a sharp increase in airprox incidents (that is near misses between drones (UAVs) and civil aircraft) and a worrying aspect of the situation is that the operator of the drone often cannot be identified. This is leading countries into requiring that all operators of drones should be registered and that their drones should carry a visible identification number that enables the owner/operator to be traced.