The federal government must pay health insurance companies roughly $12 billion that they're owed under part of the Affordable Care Act, the Supreme Court ruled Monday in an 8-1 decision.

The big picture: The ACA's "risk corridors" program was designed to help stabilize the law's insurance markets in their early years, but the Trump administration argued that Congress had prohibited it from making the required payments. The Supreme Court disagreed, saying insurers have a right to collect the money they're owed under the program.