(Reuters) - A U.S. appeals court revived a lawsuit accusing Whole Foods of illegally firing a worker who refused to remove her "Black Lives Matter" facemask and complained about racism at the upscale grocery chain.

In a 3-0 decision released on Wednesday, the 1st U.S. Circuit Court of Appeals said the firing of Savannah Kinzer, an outspoken critic who worked in a Cambridge, Massachusetts, store, "arguably deviated" from Whole Foods' disciplinary process.

The Boston-based panel also upheld the dismissal of similar claims by two other workers, Haley Evans and Christopher Michno, finding no proof that Whole Foods' discipline of them was unusual. Whole Foods is owned by Amazon.com ( AMZN ).

Neither Whole Foods nor its lawyers immediately responded to requests for comment. A lawyer for the plaintiffs did not immediately respond to similar requests.

The lawsuit is one of many arising from protests that followed the May 2020 killing of George Floyd by a Minneapolis police officer.

It began as a proposed class action over a Whole Foods dress code that barred workers from wearing Black Lives Matter attire.

Whole Foods has long maintained that its dress code, which also covered visible slogans, logos and ads, was meant to foster a welcoming, safe and inclusive shopping environment. The appeals court dismissed the class action claims in 2022.

Kinzer said she was fired in retaliation for "protected conduct" including protesting outside her store, rejecting demands to stop wearing a mask, talking to the press, and filing a complaint with the Equal Employment Opportunity Commission.

Whole Foods said Kinzer's poor attendance, including "attendance points" for wearing a mask, justified her firing.

Circuit Judge Kermit Lipez, however, said it was unclear whether Whole Foods imposed a final, decisive attendance point against Kinzer through a normal application of its time and attendance policy, or because of her protected conduct.

"It is the province of a jury to decide such a dispute," he wrote.

The appeals court returned Kinzer's case to U.S. District Judge Allison Burroughs in Boston, who dismissed all of the plaintiffs' claims in January 2023.

Whole Foods employed Evans in Marlton, New Jersey, and Michno in Berkeley, California.

The case is Kinzer et al v Whole Foods Market Inc, 1st U.S. Circuit Court of Appeals, Nos. 22-1064, 23-1100.