WASHINGTON — The Supreme Court ruled Tuesday that even videos that depict wanton animal cruelty deserve free-speech protections under the First Amendment.

In an 8-1 decision that united the court's liberal and conservative wings, the justices struck down a law that was enacted in response to so-called "crush videos," supposedly designed to satisfy bizarre sexual cravings. The court said the law, however well-intentioned, went too far.

"Maybe there are some categories of speech that have been historically unprotected," Chief Justice John Roberts Jr. wrote for the majority, "but if so, there is no evidence that 'depictions of animal cruelty' is among them."

The court's ruling means that animal cruelty won't be added to obscenity, fraud and the handful of other categories of constitutionally unprotected speech. It's also the latest example of a conservative-led court striking down an act of Congress with an expansive view of the First Amendment.

Earlier this year, by a 5-4 vote — a much narrower decision — the Roberts court likewise struck down on free-speech grounds campaign finance restrictions on corporate campaign spending.

"The majority opinion shows that the current court, although frequently described as politically conservative, continues to take free speech protections seriously," said Mayer Brown lawyer Andy Tauber, who filed an amicus brief in the case.

The court's latest ruling overturns the conviction of Robert J. Stevens, whose website, "Dogs of Velvet and Steel," offered videos showing dogfights, as well as some showing pit bulls mauling pigs.

Stevens had been convicted under a law, originally authored by Republican U.S. Rep. Elton Gallegly of California, that was incited by reports of crush videos.

"Crush videos often depict women slowly crushing animals to death 'with their bare feet or while wearing high-heeled shoes,' sometimes while 'talking to the animals in a kind of dominatrix patter' over 'the cries and squeals of the animals,' " Roberts explained, quoting in part from a congressional report.

The Obama administration, in the course of defending the law signed by former President Bill Clinton, contended that the market for crush and dog-fighting videos is growing and lucrative.

The law imposed penalties of up to five years in prison for anyone who knowingly "creates, sells or possesses a depiction of animal cruelty." Animal cruelty is defined as having "intentionally maimed, mutilated, tortured, wounded or killed" an animal, if the behavior is also illegal in the jurisdiction where it's filmed.

Numerous states — including California, Kentucky, North Carolina and South Carolina — had urged the court to uphold the law, as had animal protection groups. Book publishers and media organizations wanted the law struck down.

Solicitor General Elena Kagan, a potential Obama administration nominee to the Supreme Court, had asked the justices to balance the "value" of the speech against its "societal cost." Roberts, though, rejected that notion as "startling and dangerous."

"The First Amendment's guarantee of free speech does not extend only to categories of s peech that survive an ad hoc balancing of relative social costs and benefits," Roberts wrote.

Roberts further characterized the 1999 law as creating a criminal prohibition of "alarming breadth" and complexity. He noted, for instance, that the District of Columbia bans hunting, and he questioned whether that ban could be used to prosecute purveyors of hunting magazines.

Justice Samuel Alito was the sole dissenter. He challenged as unrealistic Roberts' claim that hunting depictions might be outlawed, and he said the law's exemptions for "educational" or "journalistic" depictions were sufficient.

Before the law was enacted, "the underlying conduct depicted in crush videos was nearly impossible to prosecute," added Alito, a former federal prosecutor.

Wayne Pacelle, the president and chief executive officer of the Humane Society of the United States, said that Congress should pass a narrower law quickly "to make sure the First Amendment is not used as a shield for those committing barbaric acts of cruelty, and then peddling their videos on the Internet."

MORE FROM MCCLATCHY

Supreme Court appears to back student group's exclusionary rules

For the next Supreme Court justice, check the playbook

GOP warns Supreme Court filibuster possible

Stevens' retirement sets up Supreme Court battle

Follow the latest legal affairs news at McClatchy's Suits & Sentences