WASHINGTON (Reuters) - The American Civil Liberties Union and groups across the political spectrum sued Washington’s Metro transit system on Wednesday, saying its ban on issue-oriented ads violated U.S. constitutional guarantees of free speech.

FILE PHOTO: A Metro subway system map can be seen in a train car window as the train leaves the station during the morning rush at the Metro Center subway station in Washington, U.S. June 12, 2017. REUTERS/Jonathan Ernst

The suit was filed in federal court in Washington by the ACLU, women’s healthcare collective Carafem, far-right commentator Milo Yiannopoulos’ company, and animal rights nonprofit People for the Ethical Treatment of Animals (PETA).

The 26-page suit alleges that the Washington Metropolitan Area Transit Authority violated plaintiffs’ rights by rejecting their ads, including one submitted by the ACLU with the text of the Constitution’s First Amendment, which guarantees freedom of speech, in English, Spanish and Arabic.

“This case highlights the consequences of the government’s attempt to suppress all controversial speech on public transit property,” the ACLU’s Arthur Spitzer, lead counsel in the case, said in a statement.

The Metro, which is the second-busiest U.S. rail transit system with an average of 682,000 daily trips, said in a statement that it would defend its ad guidelines, calling them “reasonable and view-point neutral.”

Metro also turned down a Carafem ad for abortions using medication and PETA ads urging people to “Go Vegan.” Ads for Yiannopoulos’ book “Dangerous” were accepted in June but removed a few days later after riders complained.

The lawsuit argues that four of the transit agency’s 14 ad rules violate constitutional guarantees of free speech and of due process by discriminating against ads and advertisers deemed controversial by transit officials.

Metro’s board decided in May 2015 to ban issue-oriented advertising after an anti-Muslim group, the American Freedom Defense Initiative, sought to place ads featuring a cartoon of the Prophet Mohammad.

Rules contested by the suit include barring ads intended to sway public policy and those meant to influence people over an issue on which there are different points of view.

Metro earns about $23 million a year from advertising, and ads in or on buses, in trains and in Metro stations reach more than 90 percent of people that work in the Washington area, the suit said.