(Bloomberg) -- The American Civil Liberties Union, the iconic defender of free-speech rights, faces allegations by the US labor board that it fired an employee in order to deter its own staff from speaking up about working conditions.

The advocacy group is accused of terminating a staffer for engaging in collective action about working conditions and doing so to discourage other employees from speaking up, according to a complaint before a National Labor Relations Board judge.

The discharged employee had been “concertedly complaining” about wages, hours, and working conditions “throughout 2020, 2021, and until about May 2022,” according to the filing, which was issued in March by an NLRB regional director on behalf of the labor board’s general counsel, and obtained by Bloomberg News through a Freedom of Information Act request.

“The ACLU flatly disputes these allegations and remains confident on the merits of its case,” a spokesperson for the organization said Monday in a statement, which also said the ACLU “respects and supports its employees’ right to free speech.”

In a legal filing, the ACLU argued the worker “was terminated for just cause,” and that the case should be handled through the organization’s own arbitration process. 

The ACLU also claimed the NLRB general counsel, Jennifer Abruzzo, lacks authority to issue complaints in the first place, because of the way President Joe Biden fired her predecessor who’d been appointed by Donald Trump. The group has withdrawn that argument after determining it’s a “technical, procedural issue,” according to Monday’s statement.

Many of the ACLU’s own employees have unionized in recent years, amid a broader wave of organizing by nonprofit and political advocacy staff. The fired staffer was represented by the union ACLU Staff United, which the ACLU agreed to voluntarily recognize and negotiate with in 2021 after employees signed up with the group.

Federal law protects the right of workers to communicate and protest about working conditions, with or without a union. 

Complaints issued by NLRB regional directors are considered by administrative law judges, whose rulings can be appealed to labor board members in Washington DC, and from there into federal appeals court. The agency can order companies to change illegal policies and reinstate fired activists, but lacks authority to issue punitive damages or hold executives personally liable for violations of the law.

(Updates with ACLU comment.)

©2023 Bloomberg L.P.