All ordinances passed by the board of aldermen shall be promptly delivered by the board of aldermen to the mayor. If the mayor approves any ordinance, he shall sign it. If the mayor disapproves any ordinance, he shall not sign it. The mayor shall return all ordinances to the legislative clerk within two (2) weeks after delivery to him with his approval or disapproval. Any ordinance approved by the mayor shall be law. Any ordinance disapproved by the mayor shall be returned with a message stating the reasons for his disapproval. Any disapproved ordinance shall not become a law unless subsequently passed by a favorable vote of four-fifths of the whole board of aldermen within thirty (30) days from the time of the return of the ordinance. (Acts 1951, Ch. 539, § 21; Res. No. 23-81, § 1, 5-14-81; Res. No. 17-89, 9-29-89)