People sit in the waiting room of the Indian Health Service clinic in Crow Agency, Montana, in 2008.

Native American tribes are locked in a battle with the federal government over who pays for health care in Indian country. At stake: millions of dollars in fines that many tribes say they can’t afford.

At the root of the trouble is a clause in the Affordable Care Act that requires large employers — and tribes — to provide private insurance for nearly all employees.

But some tribal leaders say that, although tribes do often employ a lot of people, buying insurance for their employees would be prohibitively expensive. Others say that options offered on the national exchange offer better services at better prices than the tribe would be able to afford.

And most frustrating of all, they say, Native Americans living on reservations already qualify for government-sponsored health services. The Indian Health Service (IHS), an agency within the Department of Health and Human Services, was set up in 1955 to provide comprehensive government-sponsored health care to all indigenous tribes.

“The United States made a commitment to the Indian tribes to provide health care to them. And yet the federal government is reneging on that,” Devin Delrow, director of federal relations at the National Indian Health Board, a Washington D.C. advocacy group, told BuzzFeed News.

Here’s the legal conundrum the tribes are fighting: The “employer mandate” within the Affordable Care Act requires them to pay for private insurance in addition to the public services the IHS provides.

But failure to comply with the ACA mandate could also be costly.

“Either way it’s going to financially cripple our tribe,” said Evelyn Espinoza, health director of the Rosebud Sioux Tribe, which has about 28,000 members in South Dakota. “It’s going to cost millions of dollars to be in compliance with this mandate — or be fined.”

Those costs would be “an added cost to the tribe in an already poverty-stricken area,” Brandon Sazue, chairman of the Crow Creek Sioux Tribe of South Dakota, which has about 3,500 members, told BuzzFeed News.

It’s not yet clear whether the IRS will impose these fines, but if it does for the Rosebud Sioux, Espinoza said, “critical services are going to be cut.”

“It would cause us to terminate maybe 500 employees. It would take away our ability to take care of our elders and our youth ” said O.J. Semans, a member of the Rosebud Sioux health board. “It would completely break us.”

Semans estimates that the annual cost to buy insurance would be $4.5 million a year, and the cost of the fines $2.5 million. The tribe can’t afford either, he said, so he worries the government would then look to seizing the Rosebud Sioux’s land. “The only item we have of any value is our land.”