Even after the monumental 2015 U.S. Supreme Court ruling Obergefell v. Hodges granted same-sex couples the right to marry, discrimination against gay and lesbians remains common, and 28 states still allow employers to fire employees for being gay.

But a new appeals court ruling may help push the fight for LGBT rights forward.

On Monday, the 2nd U.S. Circuit Court of Appeals ruled 10-3 in Zarda v. Altitude Express that federal law already prohibits workplace discrimination against gay people. Chief Judge Robert Katzmann argued that the section of 1964 Civil Rights Act barring discrimination on the basis of sex also protects gay people.

Essentially, the court concluded that discriminating against anyone because of their sexual orientation is a form of discriminating against them because of their sex.

"[S]exual orientation discrimination is a subset of sex discrimination because sexual orientation is defined by one’s sex in relation to the sex of those to whom one is attracted, making it impossible for an employer to discriminate on the basis of sexual orientation without taking sex into account," Katzmann wrote.

This is a huge win for equal rights.

According to a 2013 poll, 21 percent of LGBT people said they had experienced discrimination at work. But the Employment Non-Discrimination Act (ENDA), which would have enshrined employment protections for LGBT people, has never made progress in Congress (and is almost certain not to become law under President Donald Trump).

It looks like the Supreme Court won't be taking up the Zarda case anytime soon, so the ruling will only only apply to New York, Connecticut and Vermont, for now. But other plaintiffs are likely to cite the ruling in future cases, and the arguments that Katzmann employed in the court's decision are gaining steam. If this interpretation of the Civil Rights Act becomes widespread and adopted by other appeals courts, it would largely render ENDA unnecessary.

Monday's ruling did not address the questions of workplace discrimination against transgender people. It's easy to see, though, how the courts could also recognize the application of the Civil Rights Act to discrimination against trans individuals, using similar arguments to those employed in Zarda.