Elon Musk’s X broke the law in firing an employee who criticized management’s return-to-work policy, the National Labor Relations Board alleged, in its first formal complaint against the company formally known as Twitter.

The NLRB’s “Region 20” San Francisco branch on Friday claimed that X violated the National Labor Relations Act by terminating Yao Yue, a principal software engineer, shortly after Musk took over in late October. The NLRB alleged that X fired Yue after she attempted to organize other Twitter workers who were upset about Musk’s sudden change to the company’s work requirements.

CNBC reported that Musk sent emails to Twitter employees detailing his expectations, going so far as to say “any manager who falsely claims that someone reporting to them is doing excellent work or that a given role is essential, whether remote or not, will be exited from the company.”

“If you can physically make it to an office and you don’t show up, resignation accepted,” Musk said, according to the NLRB. That led several workers to express “concern and outrage” over the directive to return to the office immediately, according to the original legal charge document that was filed in March.

Yue then tweeted, “Don’t resign, let him fire you. You gain literally nothing out of resignation.” She also posted in a company Slack channel a message saying, “Don’t be fired. Seriously.”

Many of Yue’s colleagues responded to her messages, according to the legal charge document. Meanwhile, Musk also directed his management team to scan any online posts and Slack “in order to identify who should be fired,” the document said.

Five days later, Yue was fired and told that she was violating an unspecified company policy, the legal document said.

“Ms. Yue alleges that Twitter chose her for layoff in retaliation for her attempt to organize her co-workers not to resign, so they would have better legal footing to challenge any separation from Twitter,” the document said.

The NLRB alleges that X has “been interfering with, restraining, and coercing employees in the exercise of the rights guaranteed” under national labor law.

A spokesperson for X didn’t immediately respond to a request for comment.

“After 12 amazing years and 3 weeks of chaos, I’m officially fired by Twitter,” Yue said in a tweet on Nov. 15. “Never expected I would have stayed this long, and never expected I would be this relieved to be gone.”

The NLRB said it’s seeking to “Make Yao Yue whole for any direct or foreseeable pecuniary harm, as well as other consequential damages suffered as a result of Respondent’s unlawful conduct” in addition to providing “all other relief as may be just and proper to remedy the unfair labor practices alleged.”

A hearing on the case is scheduled for Jan. 30, in San Francisco.