California Code, Government Code - GOV § 53758.5

(a) If a court determines that a fee or charge for a property-related service, including water, sewer, and refuse collection, violates Section 6 of Article XIII D of the California Constitution, then the local agency shall, in the next procedure to impose or increase the fee or charge, credit the amount of the fee or charge attributable to the violation against the amount of the revenues required to provide the property-related service unless a refund is explicitly provided for by statute.

(b) This section does not apply to claims related to billing errors.