Michele Goodwin, a regulation professor who focuses on well being coverage on the College of California, Irvine, mentioned the requirements for successful a request to remain a judicial order could be even larger than for an enchantment. Combating for one and shedding it, she mentioned, would elevate explicit dangers of an appeals court docket choice that might take a equally slender view of what the C.D.C. could do in a public well being disaster — and that, not like a district court docket ruling, would even be a binding precedent.

“Shedding sends a really sturdy message, and never only for the matter that occurs to be at hand, however for different instances associated to public well being and security,” she mentioned.

The C.D.C. mentioned on Wednesday that masking remained vital to guard the general public well being of passengers on planes, trains, buses and subways, and a recent poll showed that 56 percent of Individuals assist the requirement. However airways have known as for an finish to the requirement for months. And except for public transportation, the administration has been intentionally shifting away from masking as a vital pandemic device for weeks.

Requested on April 11 why Mr. Biden wore a masks the earlier weekend whereas Vice President Kamala Harris had stood over him maskless at an occasion, Jen Psaki, the White Home press secretary, mentioned it was as much as every particular person to resolve what to do.

“All of us make selections. Some folks in listed here are carrying masks to make them extra comfy, or as a result of they selected to that day,” she mentioned, maybe as a result of they are going to be round relations or others who’re notably weak. “And the president makes that call, as all of us do as properly.”

In late February, the C.D.C. changed its guidelines in a approach that made it far much less probably {that a} county could be thought of excessive threat, and specified that it advisable indoor mask-wearing in high-risk areas. In areas of average threat — like Manhattan and Washington, D.C. — these who are particularly vulnerable to severe illness from the virus ought to speak to their well being care suppliers about whether or not to put on a masks, the revised guidelines say.

“Our emphasis proper now could be on getting folks data and instruments they should make selections for themselves,” Dr. Greta Massetti, a senior epidemiologist who helps lead the company’s pandemic response, mentioned in an interview final week. These decisions ought to be “primarily based on their very own private degree of threat and their threat tolerance,” she mentioned.

Sheryl Homosexual Stolberg and Katie Benner contributed reporting.