Cal. RTC § 2271

A local agency may levy, or have levied on its behalf, a rate in addition to the maximum property tax rate established pursuant to this chapter (commencing with Section 2201) to pay costs mandated by the federal government or costs mandated by the courts or costs mandated by initiative enactment, which are not funded by federal or state government.

The Controller may audit any rate imposed under this section and any data related to the establishment thereof. If the Controller determines that such rate exceeds a rate which would be necessary to meet the federally mandated, initiative-mandated or court-mandated costs, or if the Controller determines that such rate has been levied to pay any cost mandated by a court which has resulted from litigation entered into in order to avoid the property tax rate limits established by this chapter, or if the Controller determines that a local agency has erroneously concluded that it is subject to costs mandated by the courts or costs mandated by the federal government, he shall immediately notify the local agency of such determination, and the local agency shall reduce its property tax rate by an appropriate amount for the next succeeding fiscal year. In the event that a local agency fails to make such a reduction in its property tax rate, the Controller shall request the Attorney General to bring an action under Chapter 2 (commencing with Section 1084) of Title 1 of Part 3 of the Code of Civil Procedure to force a reduction in the rate.