Section 27. The board shall hear all complaints made to it against any person registered as a pharmacist charging him in his business as a pharmacist with violating any of the rules or regulations of the board or any laws of the commonwealth, and especially the laws relating to the sale of alcoholic beverages, as defined in section one of chapter one hundred and thirty-eight, and alcohol; or with engaging with, or aiding or abetting another in the violation of said rules, regulations or laws; or, if he himself is not the owner and actively engaged in such business, with suffering or permitting the use of his name or certificate of registration by others in the conduct of the business of pharmacy. Any complaints which are the result of a conviction by a court of competent jurisdiction shall be made within twelve months from the date such a conviction becomes known to the board. The board shall notify the person complained against of the charge against him and of the time and place of the hearing at which he may appear with his witnesses and be heard by counsel. It may summon witnesses and compel their attendance at said hearings. Witnesses shall testify on oath and may be sworn by a member of the board. Three members of the board shall be a quorum for any such hearing.