California Code, Government Code - GOV § 66024

(a) In any judicial action or proceeding to validate, attack, review, set aside, void, or annul any ordinance or resolution providing for the imposition of a development fee by any city, county, or district in which there is at issue whether the development fee is a special tax within the meaning of Section 50076, the city, county, or district has the burden of producing evidence to establish that the development fee does not exceed the cost of the service, facility, or regulatory activity for which it is imposed.

(b) No party may initiate any action or proceeding pursuant to subdivision (a) unless both of the following requirements are met:

(c) For purposes of this section, costs shall be determined in accordance with fundamental fairness and consistency of method as to the allocation of costs, expenses, revenues, and other items included in the calculation.