A federal appeals court on Tuesday struck down a government policy that can lead to broadcasters being fined for allowing even a single curse word on live television, saying it is unconstitutionally vague and threatens speech "at the heart of the First Amendment."

The 2nd U.S. Circuit Court of Appeals in Manhattan threw out the 2004 Federal Communications Commission policy, which said that profanity referring to sex or excrement is always indecent.

"By prohibiting all `patently offensive' references to sex, sexual organs and excretion without giving adequate guidance as to what `patently offensive' means, the FCC effectively chills speech, because broadcasters have no way of knowing what the FCC will find offensive," the court wrote.

"To place any discussion of these vast topics at the broadcaster's peril has the effect of promoting wide self-censorship of valuable material which should be completely protected under the First Amendment," it added.

The court said the FCC might be able to craft a policy that does not violate the First Amendment.

It cited several examples of chilled speech, including a Vermont station's refusal to air a political debate because one local politician previously had used expletives on the air and a Moosic, Pa., station's decision to no longer provide live coverage of news events unless they affect matters of public safety or convenience.