The American Civil Liberties Union sued the agency that runs the Metro system in Washington, D.C., on Wednesday, claiming that its rejection of several advertisements — including one from the A.C.L.U. itself — violated the First Amendment.

The ads rejected by the Washington Metropolitan Area Transit Authority, which runs mass transit services in and around the nation’s capital, included one for an abortion pill, another promoting a new book by the right-wing provocateur Milo Yiannopoulos, and yet another urging consumers to reject animal cruelty.

A fourth, submitted by the A.C.L.U. itself, consisted of little more than transcripts of the First Amendment of the United States Constitution in English, Spanish and Arabic.