Doctors sued county for the unreimbursed portion of their invoices for emergency medical treatment given to participants in the county’s health plan.  Under the Knox-Keene Act, a health plan must reimburse noncontracting health care providers for the reasonable value of the emergency care they render to health plan participants.  A provider that thinks it has been underpaid may sue a private health plan on a quantum meruit theory or under B&P Code 17200.  But this decision holds that a government agency that operates a health plan is immune from such a suit because Gov. Code 815 bars suits against government entities under common law theories such a quatum meruit.  Gov. Code 815/6 doesn’t rescue the provider’s claim because though the county owes a statutory duty to pay the reasonable value of the emergency services, reasonable value leaves the county discretion in determining the amount to be paid.