The American Civil Liberties Union on Wednesday sued the Washington Metro Area Transit Authority for refusing to display ads promoting Milo Yiannopoulos' book.

The lawsuit argued that parts of the agency's ad policies violate the First Amendment by discriminating against particular ads and advertisers deemed controversial by WMATA officials.

Metro's policies first came into place in 2015 after a set of anti-Muslim advertisements sparked controversy. Current guidelines ban ads "intended to influence members of the public regarding an issue on which there are varying opinions," ads that "support or oppose an industry position or industry goal without any direct commercial benefit to the advertiser," and ads "intended to influence public policy," among others.

The ACLU also filed on behalf of abortion provider Carafem, which specializes in family planning and abortion care, and People for the Ethical Treatment of Animals.

"This case highlights the consequences of the government's attempt to suppress all controversial speech on public transit property," Arthur Spitzer, legal director of the ACLU-DC and lead counsel in the case, said in a statement Wednesday. "The First Amendment protects the speech of everyone from discriminatory government censorship, whether you agree with the message or not."

The group argued WMATA has applied a double standard because it has accepted a wide variety of advertisements convey controversial viewpoints. It pointed to WMATA's rejection of PETA's ad for a vegan diet, while approving of an ad from a restaurant showing a tasty dish and labeled "PORKADISE FOUND." They also noted ads for a movie that showed four women ogling a male stripper were displayed at the same time it tore down ads for Yiannopoulos' book.

"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," said Lee Rowland, senior staff attorney with the ACLU.

The suit asked the court to declare portions of the WMATA advertising guidelines unconstitutional because they violate free speech rights and are unconstitutionally vague. A motion has also been filed on behalf of Milo Worldwide LLC, seeking immediate financial restitution for the ongoing loss of revenue from book sales caused by what they deem the wrongful removal of advertisements for his book.