Interestingly enough (an FYI only), in Canada both the pilot and drone are registered. The pilot has a registration # with Transport Canada that identifies the license type (basic or advanced), and any drone(s) that the pilot intends to fly must be registered, each drone being assigned a unique # that must be displayed on the bird.
In the USA, we are not quite there yet, but commercial UAV pilots are currently "registered" via. the Small UAS Rule (14 CFR part 107) Remote Pilot certification process. The FAA is planning to implement a similar training, testing, and certification process for recreational pilots, which I assume will be an online process that is easier and less expensive. So in the near future, all UAV pilots in the USA will be required to be "registered," and we will be on par with Canada (in this respect).
UAVs that weigh between 0.55 and 55-lbs are already required to be "registered," which I have indicated elsewhere is really another way to register the owner/pilot of the aircraft for liability reasons - you can't sue or hold a drone responsible for violating the law, personal injury, property damage, and other losses caused by drones. For example, shutting down an airport results in great financial loss for which the UAV operator is responsible and probably criminally negligent.
I assume that pilot registration in the USA and elsewhere is actually a process to grant flying privileges to would-be pilots that can be revoked due to noncompliance with the rules. I imagine that Local law enforcement will be involved with enforcing the rules and reporting violations to the FAA or the equivalent authority in other countries for further action such as fines, and revoking Remote Pilot privileges (see
Legal Enforcement Actions). It won't be long before local police will be asking UAV pilots to review applicable credentials, logs, etc. They already have the right, but I assume, not the training or the time.