Cal. CCP § 1021.5

Upon motion, a court may award attorneys’ fees to a successful party against one or more opposing parties in any action which has resulted in the enforcement of an important right affecting the public interest if: (a) a significant benefit, whether pecuniary or nonpecuniary, has been conferred on the general public or a large class of persons, (b) the necessity and financial burden of private enforcement, or of enforcement by one public entity against another public entity, are such as to make the award appropriate, and (c) such fees should not in the interest of justice be paid out of the recovery, if any. With respect to actions involving public entities, this section applies to allowances against, but not in favor of, public entities, and no claim shall be required to be filed therefor, unless one or more successful parties and one or more opposing parties are public entities, in which case no claim shall be required to be filed therefor under Part 3 (commencing with Section 900) of Division 3.6 of Title 1 of the Government Code.

Attorneys’ fees awarded to a public entity pursuant to this section shall not be increased or decreased by a multiplier based upon extrinsic circumstances, as discussed in Serrano v. Priest, 20 Cal. 3d 25, 49.