Any action or proceeding in which the validity of the adoption of the retail transactions and use tax ordinance provided for in this article or any of the proceedings in relation thereto is contested, questioned, or denied, shall be commenced within 90 days after the date this section becomes effective; otherwise, those proceedings, including the adoption and approval of the ordinance, are valid, and in every respect legal and incontestable.
Source:
Section 130355, https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=PUC§ionNum=130355..