Cal. Gov't Code § 3524.73

(a) Judicial review of a unit determination shall only be allowed under either of the following circumstances:
1. (1) When the board, in response to a petition from the state or an employee organization, agrees that the case is one of special importance and joins in the request for the review.
2. (2) When the issue is raised as a defense to an unfair practice complaint. A board order directing an election shall not be stayed pending judicial review.
  Upon receipt of a board order joining in the request for judicial review, a party to the case may petition for a writ of extraordinary relief from the unit determination decision or order.
(b) Any charging party, respondent, or intervenor aggrieved by a final decision or order of the board in an unfair practice case, except a decision of the board not to issue a complaint in such a case, may petition for a writ of extraordinary relief from such decision or order.
(c) The petition shall be filed in the district court of appeal in the appellate district where the unit determination or unfair practice dispute occurred. The petition shall be filed within 30 days after issuance of the board’s final order, order denying reconsideration, or order joining in the request for judicial review, as applicable. Upon the filing of the petition, the court shall cause notice to be served upon the board and thereupon shall have jurisdiction of the proceeding. The board shall file in the court the record of the proceeding, certified by the board, within 10 days after the clerk’s notice unless the time is extended by the court for good cause shown. The court shall have jurisdiction to grant to the board any temporary relief or restraining order it deems just and proper and in like manner to make and enter a decree enforcing, modifying, or setting aside the order of the board. The findings of the board with respect to questions of fact, including ultimate facts, if supported by substantial evidence on the record considered as a whole, shall be conclusive. The provisions of Title 1 (commencing with Section 1067) of Part 3 of the Code of Civil Procedure relating to writs shall, except where specifically superseded herein, apply to proceedings pursuant to this section.
(d) If the time to petition for extraordinary relief from a board decision has expired, the board may seek enforcement of any final decision or order in a district court of appeal or a superior court in the district where the unit determination or unfair practice case occurred. If, after hearing, the court determines that the order was issued pursuant to procedures established by the board and that the person or entity refuses to comply with the order, the court shall enforce the order by writ of mandamus. The court shall not review the merits of the order.