Cal. Health & Safety Code § 1371.8

A health care service plan that authorizes a specific type of treatment by a provider shall not rescind or modify this authorization after the provider renders the health care service in good faith and pursuant to the authorization for any reason, including, but not limited to, the plan’s subsequent rescission, cancellation, or modification of the enrollee’s or subscriber’s contract or the plan’s subsequent determination that it did not make an accurate determination of the enrollee’s or subscriber’s eligibility. This section shall not be construed to expand or alter the benefits available to the enrollee or subscriber under a plan. The Legislature finds and declares that by adopting the amendments made to this section by Assembly Bill 1324 of the 2007–08 Regular Session it does not intend to instruct a court as to whether or not the amendments are existing law.