"This opinion leaves the commission free to modify its current policy," Kennedy wrote, "in light of its determination of the public interest and applicable legal requirements. And it leaves the courts free to review the current policy or any modified policy in light of its content and application."

Justice Sonia Sotomayor did not participate in the decision, since she had heard the case when serving on a federal appeals court in New York, before joining her current job.

A separate appeal involving singer Janet Jackson's "wardrobe malfunction" and brief partial nudity on national television is pending at the high court. The justices are likely to throw the case back to the lower courts, in light of Thursday's ruling.

The FCC said it would begin to immediately implement the policy.

"As a matter of good governance, it is now time for the FCC to get back to work so that we can process the backlog of pending indecency complaints -- which currently stands at just under 1.5 million involving about 9,700 TV broadcasts," said Commissioner Robert McDowell, "Some of these complaints date back to 2003. We owe it to the American public and the broadcast licensees involved to carry out our statutory duties with all deliberate speed."

There was no immediate reaction from the broadcasters in the Fox and ABC cases.

But a group opposing stricter government control over TV applauded the high court's ruling.

"Today's decision by the Supreme Court re-emphasizes what we have been advocating all along: That parents, not the government, are the best arbiters of what their children should be watching on TV," said TV Watch's executive director, Jim Dyke. "In the one-third of American homes with children, parents have tools such as the V-chip and content ratings to help them make decisions about what their children watch based on the age of the child and their family's tastes and values."

The high court two years ago ruled in favor of the FCC on the issue of "fleeting expletives," concluding federal regulators have the authority to clamp down on broadcast TV networks airing isolated cases of profanity.

The court, however, refused both at that time and now to decide whether the commission's policy violates the First Amendment guarantee of free speech, ruling only on the agency's enforcement power.