Reno v. American Civil Liberties Union, 521 U.S. 844 (1997), was a landmark decision of the Supreme Court of the United States, unanimously ruling that anti-indecency provisions of the 1996 Communications Decency Act violated the First Amendment's guarantee of freedom of speech.

The American Civil Liberties Union argued that certain parts of the act were facially unconstitutional and sought a preliminary injunction preventing the government from enforcing those provisions.

The government's main defense of the CDA was that the Supreme Court had upheld similar decency laws in three prior decisions: Ginsberg v. New York (1968);[5] F.C.C.

v. Pacifica Foundation, the Supreme Court upheld the possibility of the FCC delivering administrative sanctions to a radio station for broadcasting George Carlin's "Seven Dirty Words" comedy routine.

In Reno v. ACLU, however, the Court ruled that the "time, place, and manner regulation" that Renton had enacted did not correspond with the CDA, which was "a content-based blanket restriction on speech".

"[1] The rest of the CDA, including the "safe harbor" provision in Section 230 protecting Internet service providers from being liable for the words of others, was not affected by this decision and remains law.