The plaintiff, Gerald Bostock, was fired from his county job after he expressed interest in a gay softball league at work. The lower courts followed the Eleventh Circuit‘s past precedent that Title VII did not cover employment discrimination based on sexual orientation. The case was consolidated with Altitude Express, Inc. v. Zarda, a similar case of apparent discrimination due to sexual orientation from the Second Circuit, but which had added to a circuit split. Oral arguments were heard on October 8, 2019, alongside R.G. & G.R. Harris Funeral Homes Inc. v. Equal Employment Opportunity Commission, a similar question of Title VII discrimination relating to transgender persons.
On June 15, 2020, the Court ruled in a 6–3 decision covering all three cases that discrimination on the basis of sexual orientation or gender identity is necessarily also discrimination “because of sex” as prohibited by Title VII. According to Justice Neil Gorsuch‘s majority opinion, that is so because employers discriminating against gay or transgender employees accept a certain conduct (e.g., attraction to women) in employees of one sex but not in employees of the other sex.
Source: https://en.wikipedia.org/wiki/Bostock_v._Clayton_County