but to your point as to where they can fly: they can fly in any airspace that is uncontrolled - to a max altitude of 500ft agl. otherwise you need to file for permission to fly your drone, in which case they will assign a tfr. drones over 250 grams, or more, in weight must be registered with the faa. and any drone operating for any other use than recreation, must be registered wit the faa.  plus, at night, you have to have a flashing beacon light.
United States