Home Depot must reinstate a worker who quit after they refused to remove a slogan supporting the Black Lives Matter movement from their apron, the National Labor Relations Board announced on Wednesday after it found that the worker’s actions were protected by federal law.

The ruling by the National Labor Relations Board held that Home Depot violated federal law in 2021 when it told the worker that they must quit or remove the letters “BLM,” an acronym for Black Lives Matter, that they had drawn by hand onto their apron.

The case is one of several that centered on the issue of civil rights apparel in the workplace after the police killing of George Floyd in May 2020, an episode that galvanized many workers across the country to back the Black Lives Matter movement by showing support on their work uniforms or face masks.

The National Labor Relations Board said in its ruling that Antonio Morales Jr., who worked at a Home Depot store in the Minneapolis area, was protected by the National Labor Relations Act, which guarantees the legal right of workers to take part in “concerted activities” for “mutual aid or protection.”

In its ruling, the federal agency said that the worker’s refusal to remove the “BLM” marking from their uniform was considered to be “concerted” and “for mutual aid or protection” because of earlier protests by workers at the store about racial discrimination.

Lauren McFerran, the labor board’s chairman, said in a statement on Wednesday that “it is well-established that workers have the right to join together to improve their working conditions — including by protesting racial discrimination in the workplace.”

She added: “It is equally clear that an employee who acts individually to support a group protest regarding a workplace issue remains protected under the law.”

Home Depot said in an emailed statement on Wednesday that it disagreed with the labor board’s decision.

“The Home Depot is fully committed to diversity and respect for all people,” the company said. “We don’t tolerate any kind of workplace harassment or discrimination.”

The company said in an email that it would review the labor board’s full opinion in the coming days. It was unclear whether the company planned to immediately rehire Antonio Morales Jr. or appeal.

Home Depot can still appeal the labor board’s ruling to a federal appeals court.

The employee could not immediately be reached for comment on Wednesday. It was unclear whether they had a lawyer.

Charlotte Garden, a law professor at the University of Minnesota, said in an interview on Wednesday that the labor’s decision in the Home Depot case had the potential to set a precedent in similar cases before the labor board.

“This decision is extremely important in setting out some principles for how the board is going to deal with these issues,” Ms. Garden said.

Still, other cases will depend on their own individual facts, Ms. Garden said, adding that one distinction in the Home Depot case was that the worker was wearing the “BLM” marking on their uniform as part of an effort to bring attention to racial discrimination at their store.

According to the labor board’s order, the employee began wearing the “BLM” marking in August 2020, and some time after that, they began talking to co-workers and supervisors about “subjects such as ongoing discrimination and harassment” at the store.

In one instance highlighted in the labor board’s order, the worker was told by co-worker to closely follow a Black customer shopping in the store because the co-worker said that people of Somali descent were more likely to steal.

On Feb. 18, 2021, Antonio Morales Jr. met with a Home Depot district manager who told them that wearing the “BLM” marking was against company dress code, and that they could not wear the marking on their apron.

“I know that, and I am willing to be fired over this,” they said, according to a transcript of the meeting.

Antonio Morales Jr. resigned the following day, according to the labor board.

In addition to reinstating the worker, Home Depot was also ordered to give them back pay, compensate them for any adverse tax consequences, and the store must also stop prohibiting its workers from taking part in “protected concerted activities,” such as wearing a Black Lives Matter marking on an apron.