WASHINGTON — Broadcasters anticipating a major constitutional ruling on the government's authority to regulate what can be shown and said on the airwaves instead won only the smallest of Supreme Court victories Thursday.

The justices unanimously threw out fines and other penalties against Fox and ABC television stations that violated the Federal Communications Commission policy regulating curse words and nudity on television airwaves.

Forgoing a broader constitutional ruling, however, the court concluded only that broadcasters could not have known in advance that obscenities uttered during awards show programs on Fox stations and a brief display of nudity on an episode of ABC's "NYPD Blue" could give rise to penalties. ABC and 45 affiliates had been hit with proposed fines totaling nearly $1.24 million.

Broadcasters had argued that the revolution in technology that has brought the Internet, satellite television and cable has made the rules themselves obsolete. The regulations apply only to broadcast channels.

The justices said the FCC is free to revise its indecency policy, which is intended to keep the airwaves free of objectionable material during the hours when children are likely to be watching.

The agency's chairman, Julius Genachowski, said the ruling "appears to be narrowly limited to procedural issues related to actions taken a number of years ago. Consistent with vital First Amendment principles, the FCC will carry out Congress's directive to protect young TV viewers."

It was the second time the court has confronted, but not ruled conclusively on the FCC's policy on isolated expletives. Justice Anthony Kennedy said in his opinion for the court that "it is unnecessary for the court to address the constitutionality of the current policy."

The narrow decision, coupled with the more than five months that elapsed between the argument in January and Thursday's decision, could mean that the justices struggled and failed to reach agreement on a broader outcome.

Broadcasters argue that viewers now have many options, unlike the handful of channels they had available in the 1960s and 1970s when the court last weighed in on indecency on the airwaves. In many cases, viewers don't even know when they are switching between the older broadcast channels and cable.

Still, the regulated broadcast channels provide what the government has called a safe haven of milder programming, and those channels remain dominant, even in the Internet age, the administration argued.