Mia Macy applied for a job at the Bureau of Alcohol, Tobacco and Firearms while she still identified herself as a man.
During the hiring process, Macy revealed that she was transitioning to life as a woman. Days later, the ATF said it eliminated the position. Macy later learned someone else was hired for that job.
The Equal Employment Opportunity Commission ruled the former police officer had been discriminated because of her gender identity.
"It's important because every person from this point forward falls under that federal protection and that was something that maybe I had a part in," said Macy.
"Sex discrimination is consistent. It's based on sex, whether it's treating someone different because they're female or treating someone different because they changed from male to female," said Matt Wood from the Transgender Law Center.
The ATF office in Walnut Creek did not want to comment to ABC7 News about the case. Macy says she will pursue a job at the bureau.