Cal. Welf. & Inst. Code § 16817

Notwithstanding any other provision of law, a county may enter into contracts with selected providers to provide health care services in expending funds provided pursuant to this part and Part 5 (commencing with Section 17000). The county may negotiate such reimbursement or payment arrangements it desires in such contracts. A county shall not be obligated to pay for health care services unless pursuant to a contract or the county has specifically authorized such services and agreed to payment. All such contracts shall be available for review by the department. A county may require county residents specified in this part and Part 5 to use county facilities or county selected providers. This section may not be construed to limit a county’s existing obligations to furnish health care. Any county may also elect to act jointly on a regional basis with other counties in assuming the program responsibilities.