Cal. Rev. & Tax. Code § 7270.5
Any action or proceeding filed on the basis that a tax ordinance provided for in this part or Part 1.7 (commencing with Section 7280) or the issuance of any bonds thereunder or any of the proceedings in relation thereto is contested, questioned, or denied on the basis that the tax ordinance is unconstitutional or otherwise invalid and filed for the sole purpose of contesting the validity of the district transactions and use tax, shall be commenced pursuant to Chapter 9 (commencing with Section 860) of Title 10 of Part 2 of the Code of Civil Procedure. The state shall not be made a party to the action or proceeding. That action shall not be filed more than 60 days after the approval of the enabling ordinance by the voters unless the authorizing legislation specifies a longer period. If no action is filed within that period, the tax, the bonds, and all proceedings in relation thereto, including the adoption and approval of the ordinance, shall be held to be valid and in every respect legal and uncontestable.
Ca. Rev. and Tax. Code § 7270.5