House Minority Leader Nancy Pelosi, (D-Calif.), speaks during a protest on Capitol Hill July 26 against the GOP health care plan. (Drew Angerer/Getty Images)

A federal appeals court issued a ruling Tuesday that could help preserve a key subsidy that benefits health insurers and millions of Americans under the Affordable Care Act. The ruling could make it more difficult for the White House to carry out recent threats by President Trump to cut off the payments, giving legal standing to a new set of the payments’ defenders.

The U.S. Court of Appeals for the District of Columbia Circuit ruled that a coalition of 16 state attorneys general, all of whom want to preserve the subsidies, may intervene in the appeal of a lawsuit over the fate of cost-sharing subsidies — payments the government makes to insurers on behalf of about 7 million low-income Americans who receive breaks on their health plans’ deductibles and other out-of-pocket costs.

Led by the Democratic attorneys general of New York and California, the motion that the court granted is the most recent twist in the gnarled legal and political history of the subsidies. In practical terms, the ruling could make it more difficult for the Trump administration and House Republicans to abandon the payments without a court fight.

In the days since Senate Republicans failed to pass legislation that would have overturned much of the ACA, the future of the cost-sharing payment…