SpaceX filed a complaint Thursday with the US labor inspectorate, the NLRB, to try to block it from hearing former employees who say they were fired for criticizing CEO Elon Musk, AFP reported.

According to a copy of the complaint filed in federal court in Texas, the aerospace company claims the federal agency’s actions are unconstitutional and that the hearing process violates the group’s right to a jury trial.

The complaint does not dispute the idea that the former employees were fired for asking colleagues to sign a letter criticizing Elon Musk’s behavior on social media.

According to the court document, “the open letter asked SpaceX to take certain steps to address the identified deficiencies” and referred to the investigation.

A small group of SpaceX employees used the company’s internal communications platform to send an open letter to thousands of colleagues in June 2022.

In the letter, SpaceX employees asked the company’s management to look into what they consider inappropriate comments on Twitter by the flamboyant manager, who was renamed X last summer, according to US media.