Under new state rules, California hospitals and physicians are barred from billing patients for the balance of emergency care not covered by insurers. But hospitals and physicians are protesting the rules in court. The disputes typically occur when an insured patient ends up in an emergency room that is not in his or her carrier's network, and hospitals and physicians may send insurers bills that are higher than what the insurance firms usually pay providers in their network. And insurers often balk, sending back less than the full payment.