"Sex segregated job advertising has historically been used to shut women out of well-paying jobs and economic opportunities," said ACLU Attorney Galen Sherwin in a statement. "We can't let gender-based ad targeting online give new life to a form of discrimination that should have been eradicated long ago."

In its complaint, the ACLU shows that when Facebook users are creating an ad, the platform requires them to choose whether they want the ad targeted to men, women or all. "Targeting job ads by sex is unlawful under federal, state and local civil rights laws, including Title VII of the Civil Rights Act of 1964," said the ACLU.

Facebook and its ad platform have been in hot water before. Just last month, the Department of Housing and Urban Development filed a complaint against the company for allowing advertisers to target housing ads based on gender, race, religion, accessibility and national origin. While Facebook removed the ability to target housing, credit, employment, insurance or public business ads based on race, creed, color, national origin, veteran or military status, sexual orientation or disability status in April, it disabled an additional 5,000 targeting options in its ad tool suite following the HUD complaint.

"While Facebook has recently taken some steps to prevent employment discrimination against people of various protected classes on its ad platform, Facebook has consciously decided not to stop itself or employers from targeting employment ads that exclude female users from receiving the ads," said the ACLU complaint. "Instead, Facebook has consciously retained the gender targeting tool and deployed it to send employment ads that excluded non-male users from receiving the ads."

Among the employers named in the complaint are moving, retail and construction companies, software developer Abas USA and the Greensboro, North Carolina police department.