The American Civil Liberties Union filed a free speech lawsuit on behalf of one of the nation’s most prominent right-wing provocateurs on Wednesday, arguing that Washington, D.C., transit officials violated Milo Yiannopoulos’ 1st Amendment rights by removing advertisements for his new book.

Yiannopoulos, who is British, is not the group’s only client in its lawsuit filed in federal court against the Washington Metropolitan Area Transit Authority. The ACLU’s lawsuit also objected to the agency’s decision to block ad placements for the animal rights group People for the Ethical Treatment of Animals, the abortion provider Carafem and the ACLU itself.