Health and Science

Not yet ready for primetime: Big challenge to Obamacare

U.S. Supreme Court
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Hurry up and keep on waiting.

The U.S. Supreme Court early Monday kept mum on a request that it consider a case that threatens to cripple Obamacare and end financial assistance to more than 4 million customers.

The high court's decision, or lack thereof, was being closely watched by Obamacare advocates, opponents, and the White House because of the risk the case poses to the Affordable Care Act.

Less than two hours after it didn't take action in the case, the Supreme Court relisted it for consideration at Friday's weekly conference of the court's justices. That means a vote on whether to take up the case would likely occur that day, although the decision would not be announced until Nov. 10.

The court may opt to delay taking the case until several federal appeals courts finish considering the key issue.

"I don't think it means anything yet other than, 'I'm going to have to agonize for a week,'" said Timothy Jost, an Obamacare expert and professor at Washington & Lee University School of Law.

The King case, as well as the three other essentially identical court challenges, claim federal subsidies that help most customers pay for health insurance premiums on are illegal under the ACA.

Read MoreA Tale of two Obamacare price changes, which is operated by the federal government, sells private individual insurance plans in 36 states. Open enrollment on that exchange, and on the marketplaces operated by individual states, resumes Nov. 15. For now, the subsidies on remain available.

Aetna CEO on Obamacare evolution
Aetna CEO on Obamacare evolution

The legal challenge to the subsidies, if successful, would end the taxpayer-funded assistance that helps customers afford their health coverage. It would also destroy, in states served by, the Obamacare rule that starting in 2015 requires mid- to large-sized employers to offer affordable health plans to workers or face fines.

And a successful challenge also would effectively gut in those states the mandate that requires most people to have some form of insurance or pay a tax penalty.

Both the so-called employer and individual mandates are technically hinged on the existence of the subsidies.

Obamacare opponents and advocates, who rarely agree, have said the court challenge represents the biggest threat to the ACA since the 2012 Supreme Court decision that upheld much of the law.

Read MoreWhy sticking with your health plan could cost you

Plaintiffs in the past several years have filed four separate federal lawsuits challenging the legality of the subsidies.

All four suits point to explicit language in the ACA.

The act authorizes subsidies for enrollees of a state-run health-care exchange. It does not specifically say such subsidies can be issued to enrollees on the federally run exchange

Obamacare advocates long scoffed at that argument and were dismissive of speculation that the court cases would go anywhere.

Those advocates also pointed to other language in the ACA that considered the need for a federal exchange if states didn't set up their own insurance marketplaces. They argued it would be absurd, given the law's goal of covering the uninsured, to assume it didn't intend to offer federal exchange enrollees the same help buying coverage that state exchange enrollees received.

But on a single day in July, a three-judge panel in Washington, D.C.'s federal appeals court ruled 2-1 that the subsidies were illegal, while a Virginia federal appellate panel ruled 3-0 that they are legal.

The split boosted chances that Supreme Court would step in.

But in September, the entire D.C. appeals court said it would reconsider its decision. The Obama administration is considered to have the edge with that circuit because a majority of the judges were appointed by Democratic presidents.

Read MoreEnding Obamcare subsidies: Risks vs. rewards

The plaintiffs who lost the challenge in the Virginia federal appeals court did not ask for a rehearing from the full circuit, but instead went directly to the Supreme Court. There is no automatic right to a hearing by the Supreme Court.