The National Labor Relations Board has accused Starbucks of "retaliating against" three workers involved in organizing a union and is petitioning a federal court to have them reinstated. Starbucks rejects the claims.

Why it matters: The NLRB's court filing marks the latest in what's set to be a long and costly legal battle between a union drive and the coffee chain giant, as more workers at Starbucks stores move to unionize, per CNBC.

• Starbucks CEO Howard Schultz said earlier this month that the company is "being assaulted, in many ways, by the threat of unionization," Axios' Shawna Chen writes.

Driving the news: The NLRB alleges that Starbucks "disciplined, suspended, and discharged one employee, constructively discharged another, and placed a third on an unpaid leave of absence after revoking recently granted accommodations," according to a statement from the board accompanying Friday's filing.

Of note: Starbucks told NPR Sunday that the company had "filed two unfair labor practice charges against the union Workers United to 'to protect the physical safety and emotional wellbeing' of employees and customers" and said it wanted "to make it clear that the intimidation, bullying and harassment we're seeing from some union organizers is not acceptable."

Meanwhile, Workers United said the union has "filed 80 of its own unfair labor practice charges against Starbucks across the country," NPR reports.

What they're saying: "Employees have the fundamental right to choose whether or not they want to be represented by the union without restraint or coercion by their employer," said Cornele Overstreet, regional director of the Phoenix NLRB, in the board's statement.

• "The faith of Starbucks employees nationwide in workplace democracy will not be restored unless these employees are immediately reinstated under the protection of a federal court order."
• A Workers United spokesperson accused Starbucks of "grasping at straws" with its claims against the union while "launching an unprecedented and aggressive anti-union campaign against workers, including terminating over 19 union leaders across the country," per NPR.

The other side: Starbucks said in a statement to news outlets, including Axios, on Sunday that it "wholly" disagreed with the labor board's claims, outlined in the lawsuit.

• "These partners were terminated because they violated our established policies. In some instances, they also violated state law," Starbucks said of the workers.
• "A partner's interest in union representation does not exempt them from the standards we've put in place to protect partners, customers, and the communities that we serve."
• Representatives for Workers United did not immediately respond to Axios' request for comment.

Editor's note: This article has been updated to reflect Starbucks' comment to Axios.