Cal. Welf. and Inst. Code § 14103.75
Prior authorization may be required by the director for services or items prescribed or ordered by a practitioner who has been determined by the director to have been prescribing or ordering medically unnecessary or excessive services or items for Medi-Cal beneficiaries. When this requirement has been imposed upon a practitioner, the department shall give written notice to the practitioner, and shall also give written notice identifying the practitioner to all Medi-Cal providers who may be requested by that practitioner to furnish ordered or prescribed services or items. Payment may not be denied for services or items provided pursuant to an order or prescription issued by these practitioners prior to written notification by the department that these services or items must have prior authorization. After this notice has been received, it shall be the duty of the practitioner to seek prior authorization for all ordered or prescribed services or items within the scope of the director's requirement. Where a practitioner fails to obtain prior authorization for a service or item within the scope of the director's requirement and the service or item is provided or dispensed to a beneficiary by another provider, the prescribing practitioner shall be financially responsible for payment. The department shall not deny payment to the provider for the prescribing practitioner's failure to obtain prior authorization, but shall reimburse the provider as otherwise provided by law and recover the payment from the prescribing practitioner.
Ca. Welf. and Inst. Code § 14103.75