Google’s actions amid workplace organizing efforts, including the high-profile firings of several employees, were illegal violations of the National Labor Relations Act, federal regulators said this week, Ars Technica has reported.

The National Labor Relations Board filed a formal complaint [PDF] against Google Wednesday, alleging that the company has been “interfering with, restraining, and coercing employees” to interfere with their protected concerted activity—workplace organization rights that are protected by law.

Google fired several different workers late last year amid apparent efforts to organize company employees. Four former employees who were let go last November—Laurence Berland, Paul Duke, Rebecca Rivers, and Sophie Waldman—filed complaints with the NLRB almost exactly a year ago alleging that Google’s “draconian, pernicious, and unlawful conduct” was an unlawful attempt to prevent workplace organizing.

A few weeks later, another former Google employee, Kathryn Spiers, was fired after she developed a tool for the company’s internal build of Chrome that notified Google workers of their legal rights to organize. Spiers, too, filed a complaint with the NLRB claiming that Google’s retaliation against her was unlawful.