The said board of governors shall likewise have power, in its discretion, from time to time to adopt rules, subject to the approval of the supreme court, fixing the qualifications, requirements and procedure for admission to the practice of law; and, with such approval, to establish from time to time and enforce rules of professional conduct for all members of the state bar; and, with such approval, to appoint boards or committees to examine applicants for admission; and, to investigate, prosecute and hear all causes involving discipline, disbarment, suspension or reinstatement, and make recommendations thereon to the supreme court; and, with such approval, to prescribe rules establishing the procedure for the investigation and hearing of such matters, and establishing county or district agencies to assist therein to the extent provided by such rules: PROVIDED, HOWEVER, That no person who shall have participated in the investigation or prosecution of any such cause shall sit as a member of any board or committee hearing the same.