The Commission may not revoke a registration under this chapter until it has given the registrant 21 days’ notice in writing of the grounds for the proposed revocation and an opportunity to be heard. The notice shall be served in accordance with § 12.1-19.1. Within 14 days of mailing the notice, the registrant may file with the clerk of the Commission a written request for a hearing. If a written request for a hearing is filed, the Commission shall not revoke the registration except based upon findings made at such hearing.