Justice Ruth Bader Ginsburg asked about videos of cockfighting.
“What about hunting with a bow and arrow out of season?” Justice John Paul Stevens asked.
“What if I am an aficionado of bullfights,” Justice Antonin Scalia wondered, “and I think, contrary to the animal cruelty people, they ennoble both beast and man?”
And Justice Stephen G. Breyer asked about “stuffing geese for pâté de foie gras.”
The rapid-fire inquiries came in an exceptionally lively Supreme Court argument on Tuesday in the most important free speech case this term.
The case concerns the constitutionality of a 1999 federal law that bans commercial trafficking in “depictions of animal cruelty.” The number and variety of questions suggested that most of the justices thought the law was written too broadly and thus ran afoul of the First Amendment.
In defending the 1999 law, Neal K. Katyal, a deputy solicitor general, cautioned the justices against pursuing an “endless stream of fanciful hypotheticals.”
Mr. Katyal reminded the justices that the case before them concerned videos of dogfights and that the law itself was mainly prompted by so-called crush videos, which cater to a sexual fetish. Those videos show women in high heels stepping on small animals.
But the 1999 law by its terms applies to audio and video depictions of all sorts of activities in which “a living animal is intentionally maimed, mutilated, tortured, wounded or killed” if that conduct was illegal where the depiction was sold.
The case before the court, United States v. Stevens, No. 08-769, arose from the conviction of a Virginia man for selling videos of dogfights. The man, Robert J. Stevens, was sentenced to 37 months in prison. The federal appeals court in Philadelphia last year overturned Mr. Stevens’s conviction and struck down the law on First Amendment grounds.
Patricia A. Millett, a lawyer for Mr. Stevens, urged the justices to follow suit, saying the law could not be rendered constitutional by narrowing it through judicial interpretation.
“There is interpreting and then there is alchemy,” Ms. Millett said, “ and I think this statute requires alchemy.”
The law does exempt materials with “serious religious, political, scientific, educational, journalistic, historical, or artistic value.”
But several justices indicated a discomfort with the vagueness of that standard and with entrusting the question of a work’s “serious value” to prosecutors and juries.
“Could you tell me what the difference is between these videos and David Roma’s documentary on pit bulls?” Justice Sonia Sotomayor asked Mr. Katyal, referring to “Off the Chain,” an exposé of dogfighting. “David Roma’s documentary had much, much more footage on the actual animal cruelty than the films at issue here.”
Mr. Katyal responded that “the line will sometimes be difficult to draw.”
Justice Scalia said the law violates the First Amendment by treating speech condemning depictions of animals fighting more favorably than speech celebrating the fighting. Mr. Stevens’s “message is that getting animals to fight is fun,” Justice Scalia said.
The hypothetical Human Sacrifice Channel came up late in the argument. Justice Alito described how it would work.
“Suppose that it is legally taking place someplace in the world,” he said. “I mean, people here would probably love to see it. Live, pay per view, you know, on the Human Sacrifice Channel.”
Ms. Millett haltingly said that Congress could not ban such a channel solely on the ground that it was offensive.
Mr. Katyal, to the apparent surprise of some of the justices, agreed, saying the First Amendment would not permit a law banning such a channel unless it could be shown that the depictions made the sacrifices more likely. The distastefulness of the depictions alone would not justify the ban.
The justices did not seem inclined to expand categories of speech outside the protection of the First Amendment, notably obscenity and child pornography, to encompass violent images unrelated to sex.
In child pornography, Justice Ginsburg said, “the very taking of the picture is the offense — that’s the abuse of the child.” In dogfighting, by contrast, she continued, “the abuse of the dog and the promotion of the fight is separate from the filming of it.”
Ms. Millett agreed. “If you throw away every dogfighting video in the country tomorrow,” Ms. Millett said, “dogfighting will continue.”
Justice Breyer suggested that Congress would be able to draft a more carefully tailored law focusing on crush videos and the kinds of animal cruelty that are illegal in all of the states.
“Why not do a simpler thing?” Justice Breyer asked. “Ask Congress to write a statute that actually aims at those frightful things it was trying to prohibit.”
“I am not giving Congress advice,” he added, “though I seem to be.”