The U.S. Justice Department said it would appeal a Florida judge’s ruling that threw out a mask requirement for plane and air travel, setting up a likely court battle that could extend past the midterm elections.  

The department on Wednesday filed papers in Tampa, where the ruling was handed down on Monday, notifying the court of its plans to appeal. The filing was signed by Brian Boynton, principal deputy assistant attorney general.

The department said it made the move following a request from the U.S. Centers for Disease Control and Prevention.

“It is CDC’s continuing assessment that at this time an order requiring masking in the indoor transportation corridor remains necessary for the public health,” the agency said in the assessment released Wednesday evening. “CDC believes this is a lawful order, well within CDC’s legal authority to protect public health.”

U.S. District Judge Kathryn Kimball Mizelle’s revocation of the national mask mandate left confusion in its wake: while many airlines announced they would no longer require face coverings, some transit operators—including in New York City—have left the rules in place.

Leslie Manookian, a onetime Goldman Sachs Group Inc. banker whose Health Freedom Defense Fund filed the suit last April, said in an emailed statement that “we are confident that Judge Mizelle’s meticulous, thorough, and well-reasoned ruling will stand.”

A key priority of the Biden administration is to protect what power it has left to enact a mandate months from now if there’s another surge in Covid-19 cases, administration officials said Tuesday, speaking on the condition of anonymity.

The Justice Department will criticize Mizelle’s “extremely narrow” and strict reading of the 1940’s statute cited by the CDC to establish its authority to issue the mandate, said Carl Tobias, a professor at the University of Richmond School of Law.

The decision also “lacks support” for her reading of the Administrative Procedures Act and what it requires of the CDC in the context of a mask mandate, according to Tobias.

The government “will also argue that judges must defer to agency expertise on science, health and medicine about which CDC has the expertise in the midst of the worst outbreak in a century, so CDC must have the tools needed to combat the pandemic,” Tobias said.

The Justice Department had said that it stood ready to appeal the ruling, but that it would do so only “subject to the CDC’s conclusion that the order remains necessary for public health.”

On Tuesday, an administration official said the CDC would shift the focus of the existing two-week review of the masking policy—announced before the court ruling—to determine whether to appeal, instead of whether to extend the order again, as it was first conceived.  

Mizelle, among the youngest federal judges, was nominated by Donald Trump and confirmed by the Senate in November 2020. Her ruling made her an instant hero in conservative circles.

Mizelle’s ruling, while momentous, is just one front in the culture war over the pandemic response, in which conservative groups have fought what they say are onerous public health measures and pursued legal challenges to rein in the agency’s authority.

“If they appeal and lose, the CDC could end up powerless to take some basic public health precautions in the event of a surge in cases in the fall or winter,” Andy Slavitt, a former Covid response team official for the Biden administration, said before the appeal was announced. With a slew of Trump-appointed judges, he said, “that concern has to weigh on them.”

By filing an appeal, the administration would open an avenue for tossing out a ruling that could serve as a precedent constraining the CDC down the road. In a 1950 decision known as U.S. v. Munsingwear, the Supreme Court said lower courts can set aside rulings in cases that have become legally moot because of changed circumstances. Once the CDC says the mask mandate doesn’t need to be extended, then the administration can argue the issue is moot and ask the appeals court to throw out the Florida judge’s ruling.

Peter Pitts, co-founder of the Center for Medicine in the Public Interest and a former associate commissioner at the Food and Drug Administration, on Wednesday night called the appeal a “bad decision.”

“It’s the wrong public health decision and will only harden the position of those who don’t trust the CDC,” Pitts said in an interview. 

The government should have at least appealed right away in order to signal to the transportation industry and the public that it stood firmly behind the ongoing need for the mandate, he added.

“The only thing harder than getting people to wear masks is getting them to put them back on,” Pitts said.