Cal. Code of Civil Procedure § 2017.220

(a) In any civil action alleging conduct that constitutes sexual harassment, sexual assault, or sexual battery, any party seeking discovery concerning the plaintiff’s sexual conduct with individuals other than the alleged perpetrator shall establish specific facts showing that there is good cause for that discovery, and that the matter sought to be discovered is relevant to the subject matter of the action and reasonably calculated to lead to the discovery of admissible evidence. This showing shall be made by a noticed motion, accompanied by a meet and confer declaration under Section 2016.040, and shall not be made or considered by the court at an ex parte hearing. (b) The court shall impose a monetary sanction under Chapter 7 (commencing with Section 2023.010) against any party, person, or attorney who unsuccessfully makes or opposes a motion for discovery under subdivision (a), unless it finds that the one subject to the sanction acted with substantial justification or that other circumstances make the imposition of the sanction unjust.