For any violation by any pilot of any of the provisions of this chapter, or any of the rules and regulations established by the commission under the authority conferred upon the said commission by the provisions of this chapter, or under any authority which may be hereafter conferred upon said commission, the said commission may suspend or revoke the license or branch of such pilot so violating the law or such rules and regulations of said commission. The secretary of said commission shall notify such pilot in writing of the specific charge preferred against him, specifying with reasonable certainty the law or rule or regulation violated, the manner in which the same was violated, and the time and place of such offense, and shall by direction of the commission fix the time for hearing of said charges not less than five nor more than 30 days from the date of such notice. At the time and place set forth in said notice, such pilot may appear in person or by counsel, thereupon the said commission shall hear and determine the said charges. The commission may subpoena witnesses, such subpoenas to be served under the seal of said commission, and attested by the signature of the secretary, and shall be served by the Sheriff of Mobile County, or the Sheriff of Baldwin County, according to the residence of such witnesses. The fees of the sheriff for serving such subpoenas shall be paid out of the funds of said commission.