SAN FRANCISCO — In a unanimous decision that could have ripple effects across California’s health care industry, the state Supreme Court has ruled that health plans like Aetna and Blue Shield can be sued over unpaid medical bills even if the plans passed financial responsibility to third parties.

The court’s opinion Monday in Centinela Freeman v. Health Net of California is a blow to health care plans and the so-called “risk bearing organizations,” or RBOs, that they regularly contract with in order to share the financial risk they take on in covering patients’ emergency medical expenses.