Cal. Welf. & Inst. Code § 14115.1

The department may not require that any hospital based physician submit a combined charge, which includes the physician and hospital charge, if it is not the customary practice of such physician to submit a combined charge. The physician’s right to bill independently shall be respected by the department; provided, however, this shall not prevent the department from enacting reasonable regulations to insure that the total charges, when a hospital and physician bill separately, do not exceed the total charge when both bill for the same services in a combined charge.