Health and Safety Code-Division 2-Chapter 2.2. Health Care Service Plans-Article 5. Standards
No overpayment request solely because of contract with another health care service plan
Most Favored Nation, Overpayments / Recoupments
No health care service plan, including a specialized health care service plan, shall request reimbursement for overpayment or reduce the level of payment to a provider based solely on the allegation that the provider has entered into a contract with any other licensed health care service plan for participation in a benefit plan that has been approved by the director.
See https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=HSC§ionNum=1371.2.