Columbia Referendum ordinance (Charter § 128)

The voters shall have power to approve or reject at the polls any ordinance passed by the council, or submitted by the council to the voters , excepting emergency ordinances as provided for in Section 15 of this charter, ordinances for the levying of taxes, or for the issuance of special tax bills, as provided in this charter, such power being known as the referendum. Ordinances submitted to the council by initiative petition and passed by the council shall be subject to the referendum in the same manner as other ordinances. Within twenty (20) days after the enactment by the council of any ordinance which is subject to referendum, a petition signed by registered voters of the city equal in number to at least twenty-five (25) per cent of the number of votes cast for council member-at-large at the last municipal election may be filed with the city clerk, requesting that such ordinance be either repealed or submitted to the voters; provided, however, that the number of signatures in such case be not less than five hundred (500).