Section 21A. Except as hereinafter provided, no member of a municipal commission or board shall be eligible for appointment or election by the members of such commission or board to any office or position under the supervision of such commission or board. No former member of such commission or board shall be so eligible until the expiration of thirty days from the termination of his service as a member of such commission or board.
The provisions of this section shall not apply to a member of a town commission or board, if such appointment or election has first been approved at an annual town meeting of the town.