Metro Center entrance at 13th and G Streets, N.W., in Washington, D.C. Photo: Diego M. Radzinschi/ALM

The ACLU and conservative commentator Milo Yiannopoulos are not usually on the same side of an issue, except when it comes to free speech on the subway system in Washington, D.C.

The company owned by the former Breitbart news editor, MILO Worldwide and the American Civil Liberties Union, along with a women’s health collective called Carafem and the nonprofit People for the Ethical Treatment of Animals, filed a lawsuit Wednesday in federal court against the Washington Metropolitan Area Transit Authority. The lawsuit claims the D.C. subway system, called Metro, violated each groups’ First Amendment rights by refusing to run their advertisements. Metro’s advertising restrictions are “explicitly viewpoint-discriminatory,” the lawsuit claims.

“The ACLU and Mr. Yiannopoulos probably do not find themselves allied frequently, but they are allied on the First Amendment,” said Stephen Meister, a partner in the New York office of Meister Seelig & Fein, who represents MILO Worldwide.

Sherri Ly, a spokeswoman for Metro, said in an emailed statement that the transit system’s board of directors made changes to the guidelines in 2015, which included a blanket prohibition on issue-oriented ads.

“WMATA intends to vigorously defend its commercial advertising guidelines, which are reasonable and viewpoint neutral,” Ly said.

According to the lawsuit, Metro agreed to run advertisements for Yiannopoulos’ new book, “Dangerous,” from June 26 to July 23. Metro removed the ads on July 6 after complaints from riders. Metro said the displays violated its guidelines against advertisements that attempt to “influence members of the public regarding an issue of which there are varying opinions” and advertisements intended to “influence public policy.” The groups also asked the court for a preliminary injunction requiring Metro to repost the ads.

Yiannopoulos came under fire from liberals over his far-right views and news coverage while at Breitbart. Still, the lawsuit claims the ad for his book showed only a picture of Yiannopoulos’ face, the book’s title and quotations from book reviews calling the author “the ultimate troll” and “the most hated man on the internet,” among others. Meister said Metro clearly violated his client’s rights by removing the ads solely because the agency may disagree with the content of the book.

“I think this is open and shut, black and white, and I believe the court will vindicate these free speech rights,” Meister said. “D.C. Metro should be ashamed of its conduct and should not be allowed to get away with this kind of censorship.”

The ACLU and other plaintiffs claim their own advertisements, which focused on rights of free speech, vegan diets and access to birth control and abortion medication, were illegally rejected outright by Metro.

“The four plaintiffs in this case perfectly illustrate the indivisibility of the First Amendment,” said Lee Rowland, senior staff attorney with the ACLU, in a written statement. “In its zeal to avoid hosting offensive and hateful speech, the government has eliminated speech that makes us think, including the text of the First Amendment itself. The ACLU could not more strongly disagree with the values that Milo Yiannopoulos espouses, but we can’t allow the government to pick and choose which viewpoints are acceptable.”