
Registration.
Only the responsible will register, those who don't are either unaware of the need or they plan on doing something bad.
The list will not help the police when an unregistered owner does something bad, they'll likely target the innocents on the list because they live in the area of the incedent, meaning drone owners will have to account for their whereabouts at all times.
Also, what if a registered owner is flying their drone in a certain area and an unregistered owner causes an incedent with theirs in the same area and at the same time - the registered owner will need strong evidence to prove their innocence, whilst the unregistered owner will likely get off scott free because the police don't have them on the list...