SpaceX in the lawsuit filed in Brownsville, Texas federal court claims the structure of the National Labor Relations Board (NLRB), which issued a complaint against the company on Wednesday, violates the US Constitution.

The NLRB alleges SpaceX violated federal labour law by firing eight workers in 2022 for signing onto the letter, which accused Musk of making sexist comments that went against company policies. That case will be heard by an administrative judge and then a five-member board appointed by the US president. The board’s decisions can be appealed in federal court.

But SpaceX in its lawsuit claims that because federal law only allows board members and administrative judges to be removed for cause, and not at will, the NLRB’s structure is unconstitutional.

The lawsuit seeks to block the NLRB case from moving forward.

An NLRB spokesman declined to comment.

SpaceX recently utilised a similar tactic to block an administrative case by the US justice department claiming the company illegally refused to hire refugees and asylum recipients.

A federal judge in Brownsville, where Thursday’s case was filed, in November paused the administrative case pending the outcome of a lawsuit by SpaceX. The judge said that the US Constitution required administrative judges at the justice department to be appointed by the president, and not the attorney general as they currently are.

The NLRB is already facing a similar lawsuit from a Starbucks Corp employee who opposed the unionisation of the New York store where she works. The worker sued the board in October after it denied her petition for an election to dissolve the union. The agency has not responded to that lawsuit.