Fox and CBS’s First Amendment challenge to regulations against on-air profanity could either open the way to more cursing on network television or encourage broadcasters to play it safer with tamer programming.

The 2nd U.S. Circuit Court of Appeals, which sits in New York City, will hear arguments today in a case brought by the networks against the Federal Communications Commission. The networks are challenging recent government efforts to police on-air indecency more aggressively.

In legal papers, Fox and CBS cast the dispute as one of the most significant challenges to the government’s power to police the airwaves for profanity since the U.S. Supreme Court upheld its authority to do so nearly 30 years ago. That 1978 Supreme Court case, which involved a radio broadcast of a monologue by comedian George Carlin, left open the question of whether the FCC can regulate the isolated, passing use of an offensive word during a broadcast.

The case being heard today involves two instances when the FCC found that unscripted cursing during the broadcasts of two awards shows constituted “indecent” or profane” material.

In legal papers, Fox claims that the FCC “has lost sight of what the First Amendment demands” since it initiated a new policy in 2004 that considers even isolated and unscripted on-air curses by network broadcasts before 10 p.m. to be actionable offenses. The news organizations say they have been taken by surprise and that the FCC’s new position reverses decades of government deference to broadcasters.

Those curse words have become potentially much more expensive for networks since a recent law increased the maximum FCC fines tenfold, to $325,000. Because the FCC can seek to fine each network affiliate that broadcasts the offending material, Fox claims that a single expletive in its programming could conceivably cost it $65 million in fines, according to court papers.

“The result is the end of truly live television,” attorneys for Fox say in a brief.

It is a view held not only by the networks, but at least two former FCC officials who have filed a friend of the court brief on behalf of the networks. They argue that the FCC’s aggressive enforcement efforts could discourage networks from continuing their current programming.

“Prime time viewers may soon experience a sense of déjà vu as television programming reverts to the genre of “Leave It to Beaver,” according to an FCC commissioner between 1974 and 1976, Glen Robinson, and a former FCC general counsel, Henry Geller.

In court papers, the FCC has told the court that it has a compelling interest to protect minors from indecent broadcasts.

“The Court should uphold the Commission’s reasonable assessment that contemporary community standards for the broadcast medium, however loosely viewed, simply do not permit entertainers gratuitously to utter the ‘F-Word’ and the ‘S-Word’ in awards shows broadcast on national television at a time when the substantial numbers of children are certain to be in the viewing audience,” lawyers for the FCC wrote in a brief to the court.

In its briefs, the FCC suggests that it takes into consideration a distinction between types of programming when deciding whether to rule that a curse word was objectionable. The FCC suggests that it would be more hesitant to proceed against a news program for on-air cursing, and points out that it it recently dropped its case against CBS for an interview on the “The Early Show” for that very reason.

The cases before the panel of the 2nd Circuit today involve Fox’s broadcasts of the 2002 and 2003 Billboard Music Awards during which an award recipient, Cher, and an award presenter, Nicole Richie, each cursed. Despite a five-second broadcasting delay, Fox did not manage to keep the foul language from being broadcasted to millions of viewers across much of the nation. The FCC has not pursued a fine against Fox for the two broadcasts, although it issued a final ruling last month that they contained “indecent” or “profane” material.

Legal observers say it is not clear whether the 2nd Circuit will decide that desultory remarks by pop figures pave the way for a First Amendment case of major proportions.

A professor of entertainment law at the University of California, Los Angeles, Jerry Kang, said broadcasts have traditionally received less First Amendment protections than other forms of speech, partly because they are so easily accessible to children.

Mr. Kang described the case as a “legitimate First amendment question.” But he cautioned that “substantial First Amendment doctrine would have to change before the FCC lost this case.”

Still, Mr. Kang said the court could rule against the FCC by finding that the new enforcement policy is too vague, a claim that the networks have raised.

Another legal observer said the case presents an important question. The courts have not made clear whether networks should be held liable for offensive material that “slips into” certain types of programming without networks’ consent, a law professor at Harvard University, Charles Fried, said.

“The decency standard cannot be used so that it precludes proper programming which may have the occasional and unplanned incidental bad thing in it,” Mr. Fried said.

The three judges who will hear today’s arguments are Rosemary Pooler, Pierre Leval and Peter Hall. The court is allowing the arguments to be taped by C-Span. Since that is a cable rather than a broadcast network, it is not subject to the FCC regulations, and thus would not be subject to fines if it airs any profanity that is used during the court hearing.