Section 21. Refusal to Issue Certificates for Certain Causes. —

The Board shall refuse to issue a certificate of registration to any successful examinee or to any examinee registered without examination who has been convicted by a court of competent jurisdiction of any criminal offense involving moral turpitude or has been found guilty of immoral or dishonorable conduct after investigation by the Board, or has been declared to be of unsound mind. The reason for the refusal shall be set forth in writing.