The Trump administration will argue in court Tuesday that federal law does not protect gay workers from employment discrimination.
The Justice Department is supporting a New York skydiving company, Altitude Express Inc, being sued by former instructor Donald Zarda.
The instructor is accusing the company of firing him after he told a customer he was gay and she complained.
The case will require the 2nd U.S. Circuit Court of Appeals to decide whether discrimination against gay workers is a form of unlawful sex bias under the Civil Rights Act. That law bans discrimination based on workers’ sex, race, religion and other traits.
The Trump administration’s involvement in the lawsuit is one of several moves it has made that has alarmed LGBT groups.
In August, Trump signed a memorandum directing the U.S. military not to accept transgender men and women as recruits.