Rocket maker SpaceX on Tuesday will appear before a US labour board judge to face claims that it fired eight engineers for criticising CEO Elon Musk and accusing him of sexist conduct in a letter to company executives.

The case before National Labor Relations Board Administrative Law Judge Sharon Steckler in Los Angeles prompted SpaceX to file a lawsuit in January seeking to block it from going forward by claiming the board’s in-house enforcement proceedings violate the US Constitution.

The NLRB’s general counsel, which acts as a prosecutor, claims SpaceX violated US labour law by firing the engineers in 2022 after they circulated a letter accusing Musk of sexist conduct and claiming the company tolerated discrimination against women.

SpaceX is accused of violating the National Labor Relations Act, which protects workers’ rights to band together and advocate for better working conditions.

The engineers have separately filed complaints with a California civil rights agency accusing SpaceX of tolerating sex discrimination and retaliating against workers who complained.

SpaceX has denied wrongdoing while attacking the labour board’s core functions in the lawsuit, which it filed in Texas federal court. A judge last month transferred the case to California, citing the fact that the labour board case was being heard there.

SpaceX is challenging that decision in an appeals court, and the California judge on Monday sent the case back to Texas pending the outcome of the appeal.

Kayla Blado, a spokeswoman for the board, said Tuesday’s hearing “will be mostly procedural,” focusing on the scope of subpoenas the board can issue to obtain information from SpaceX and a schedule for future hearings. Steckler will not hear testimony or opening statements, Blado said.

If SpaceX loses, it could be ordered to reinstate the workers and compensate them for lost pay and benefits. Steckler’s decision in the case can be appealed to the five-member board and then a federal appeals court.

SpaceX did not respond to a request for comment. The company is represented by lawyers from law firm Morgan Lewis & Bockius including John Ring, who was the chairman of the NLRB during the Trump administration.

SpaceX had asked to put off the hearing pending the company’s bid in the Texas court to block the labour board case from moving forward. An NLRB regional director last month denied that motion and the five-member board, which has one vacancy, upheld that decision in a single-page ruling.

In its lawsuit, the company claims the labour board’s administrative process for hearing cases involving illegal labour practices violates its constitutional right to a jury trial. SpaceX also says limits on the president’s ability to remove administrative judges and board members are unconstitutional.

Starbucks, Amazon.com and Trader Joe’s, all of which are facing nationwide union organising campaigns, have raised similar arguments in pending board cases.

The labour board has said in court filings that removal protections similar to those for board judges and members have been upheld by the US Supreme Court and that the right to a jury trial does not extend to cases brought under federal labour law.