The Answer is to legislate in the same way as Aircraft that require Pilots.
1. The Drone/UAV must hold a certificate of Airworthiness.
2. The operator/Pilot must complete a recognised course and hold the appropriate licence.
3. And if the Drone/UAV is being used in a commercial sense - an Air Operators Certificate must be obtained. And the Pilots must obtain a commercial licence.
4. Lastly it should be enforced that the companies or manufacturers of these products are not permitted to sell these Airborne devices - unless the purchaser can prove that he/she complies with the above.