This presents a problem in which authorities cannot ID the drones just by looking at it. However according to a report from Bloomberg, that could change as US aviation regulators have proposed that drones in the future need to come equipped with a visible license plate, similar to that of a car.
This means that at a distance and with some equipment like binoculars, authorities should be able to ID the drone remotely to check whether or not it is registered. “This action would require small unmanned aircraft owners to display the unique identifier assigned by the FAA upon completion of the registration process on an external surface of the aircraft. Small unmanned aircraft owners would no longer be permitted to enclose the unique identifier in a compartment.”
It is unclear as to what might have prompted this proposal, but given that there are still issues of drones being used illegally and flown into restricted air spaces, making drone owners more accountable will hopefully curb that.