State officials and Minnesota health insurers are encouraging sign-ups through the MNsure exchange despite arguments Tuesday at the U.S. Supreme Court over the future of the federal Affordable Care Act.

A final decision isn't expected until next year in the court case, which argues the federal health law is unconstitutional because Congress zeroed out the statute's tax penalty for individuals who don't buy mandated coverage.

Some health care stocks gained value Tuesday after questioning by justices suggested the court would not strike down the Affordable Care Act (ACA), which launched in 2013 government-run insurance exchanges including MNsure as online marketplaces for coverage.

Legal challenges to the law over the years have created uncertainty for consumers, yet signing up for health insurance is the only way to ensure comprehensive coverage for 2021, said Nate Clark, the chief executive of the state's MNsure exchange, during a call with reporters.

"As of today, the ACA is the law of the land and so our assumption is that all consumers who want to be covered should come through open enrollment," Clark said. The sign-up period started Nov. 1 and ends Dec. 22.

Nonprofit health plans that sell coverage in Minnesota's individual market reinforced the message on Tuesday.

Officials with Minnetonka-based Medica said in a statement that it's "extremely unlikely that the Supreme Court would render any decision that would immediately impact coverage or the availability of subsidies."

Major components of the ACA should remain in place, according to officials at Bloomington-based HealthPartners. They added in a statement: "In the meantime, there is no impact to insurance coverage now, and we encourage members to continue to sign up."

The Supreme Court case hinges on whether the health law's mandate for individuals to buy coverage is "severable" from the rest of the law, Stephen Tanal, an analyst with SVB Leerink, wrote in a note to investors Tuesday. While states fighting the law argue it's not severable, that perspective was met with apparent skepticism, Tanal wrote, from justices including Brett Kavanaugh, who joined the court in 2018.

"Of the six justices who voted to uphold the law in 2015 ... five remain on the court," he wrote. "We therefore believe it to be relatively likely that [the Supreme Court] will uphold ACA by a vote of 5 or more of the 9 seated justices."

In September, about 104,000 people were buying individual market coverage through MNsure. The plans provide insurance for people who are self-employed or don't get coverage from their employer.

People also use MNsure to see if they might qualify for state public health insurance programs for those with lower incomes. About 53% of households buying individual market coverage through MNsure use premium tax credits provided through the health law.

MNsure is projecting that individual market enrollment will hold steady next year, Clark said. Economic instability with the coronavirus pandemic means that more people are holding onto coverage throughout the year, he said.

"There's nothing like a public health emergency," Clark said, "to help folks understand and appreciate the importance of having comprehensive coverage."

This fall, MNsure announced that individual market consumers in 80 counties next year will see three or more health insurance companies competing on the government-run exchange — up from 31 counties this year. Average premium increases from returning carriers will range from 1 to 4%, according to the state Commerce Department.

Christopher Snowbeck • 612-673-4744