Earlier this week, the U.S. Supreme Court refused to hear an appeal of Jesus Castillo's 2000 obscenity conviction for selling a comic book. The court let stand his sentence of 180 days in jail, a year of probation and a $4,000 fine.

Although the decision is unsurprising, given how few cases the court agrees to review, it leaves a dangerous precedent unchallenged. As of now, comic books are the only medium of artistic expression without the presumption of First Amendment protection. Why? Because comic books "are for kids."

In September 1999, Castillo, manager of Keith's Comics in Dallas, sold a copy of "Demon Beast Invasion: The Fallen" No. 2 to an undercover police officer. The adults-only comic (an English translation of a Japanese manga) was labeled as such and was stocked in an adults-only section of the shop. The police officer was an adult. Several months later, as the Dallas Observer reported, police arrested Castillo and charged him with a Class A misdemeanor, punishable by up to two years in prison plus fines.

During Castillo's trial, the Comic Book Legal Defense Fund provided expert witnesses to testify as to the offending book's artistic merits. Susan Napier, an associate professor of Asian Studies at the University of Texas at Austin, explained that "Demon Beast Invasion," far from being simply a sex comic, is filled with symbolism and political themes.

Prosecutors didn't bother to cross-examine Napier, even though she had deflated their obscenity case. Under U.S. law, for a work to be obscene it must lack any serious literary, artistic, political or scientific value when taken as a whole.

As it turned out, prosecutors didn't need to cross-examine Napier. They simply ignored her and told jurors to do the same.

"I don't care what kind of testimony is out there," the prosecuting attorney said. "Comic books, traditionally what we think of, are for kids."

Mind you, kids had nothing to do with it. It was an adult comic kept with other adult comics and sold to an adult. It either was obscene, in which case selling it to an adult would be just as illegal as selling it to a child, or it was not. Unable to prove that the book was obscene, the prosecuting attorney deliberately muddied the issue. And the jury, made up of people too stupid to get off jury duty, fell for it.

Obscenity laws by themselves are bad enough. The problem with them is that you can never know that you've run afoul of them until it's too late. Because the only standard for obscenity is the "community standard" set by the jury that hears your case after you've already either broken the law or not. But the Castillo case is worse.

"This case bodes badly for the First Amendment," said CBLDF Director Charles Brownstein. "(T)he Supreme Court has allowed a precedent to stand that allows a man to be convicted of obscenity charges without adequate proof being presented that the work he is convicted for selling is constitutionally obscene. All because the medium the alleged obscenity was placed in 'is for kids.' "

The same argument could apply to animated cartoons as well. An animated version of "Demon Beast Invasion" is available on DVD and sold in many chain video stores. And, as "everyone knows," cartoons "are for kids."

Jesus Castillo's story has many villains: a politically motivated prosecutor, a clueless vice cop and the dumbest jury since the O.J. Simpson verdict. But the main villain is the pernicious idea that comic books are only for children. That has never been the case. Comics achieved their widest circulation during World War II, when U.S. troops abroad looked forward to care packages filled with cigarettes and issues of "Superman" and "Captain Marvel."

And with publishers always seeking new audiences, it certainly isn't the case now.