As reported here on Bloomberg, a conservative activist group has filed a lawsuit, Crest v. Alex Padilla, in California state court on behalf of three California taxpayers seeking to prevent implementation and enforcement of SB 826, California’s Board gender diversity legislation. This appears to be the first litigation filed to challenge the new law. Framed as a “taxpayer suit,” the litigation seeks to enjoin Alex Padilla, the California Secretary of State, from expending taxpayer funds and taxpayer-financed resources to enforce or implement the law, alleging that the law’s mandate is an unconstitutional gender-based quota and violates the California constitution.
I don't know enough about taxpayer standing under California constitutional law to know whether the lawsuit will survive a standing challenge. Nor do I know enough about equal protection law under the California constitution to know if the suit has substantive merit.
Interestingly, the issue about which I do know something is not involved in the suit:
Interestingly, there was no challenge to the legislation as a violation of the “internal affairs doctrine,” which generally provides that the law of the state of incorporation governs those matters that pertain to the relationships among or between the corporation and its officers, directors and shareholders. The new gender diversity mandate would likely be viewed as a matter of internal corporate governance, and Section 2115.5 of the new law purports to make the mandate expressly applicable to foreign corporations with outstanding shares listed on a major U.S. stock exchange—to the exclusion of the law of the jurisdiction in which the foreign corporation is incorporated. Of course, because of standing issues, different plaintiffs would have been required to make a claim of that nature.