Appellate Judge Consuelo Callahan says overturning the district court would mark a significant expansion of the kind of material that federal courts have traditionally regulated.
Children in California who want to buy or rent a violent video game without a parent's permission could have that right taken away by a federal appeals panel, which heard arguments on the case Wednesday.
A state law passed in 2005 that tries to limit access to such games is under consideration by a three-judge panel of the 9th U.S. Circuit Court of Appeals.
The state law, which prohibits the sale or rental of the games to anyone under 18 and requires them to be clearly labeled, was struck down last year by a lower court. Video game manufacturers argued that it violates minors' First Amendment rights. Courts in several other states have struck down similar laws.
But California Deputy Attorney General Zackery Morazzini asked the federal appeals panel to uphold the law, saying violent games are just as obscene as the sexually explicit material limited from children by the U.S. Supreme Court.
He said states have every right to help parents who want to keep their children from playing violent video games.
The Video Software Dealers Association and Entertainment Software Association say imposing restrictions on video games could lead to states seeking limited access to other material under the guise of protecting children.
"Maybe a state will say we shouldn't let you sell, without a parent's permission, books about homosexuality or sex education or birth control," Paul Smith, the industry's attorney, told reporters after the hearing. "I think it's a very scary prospect."
The judges appeared to agree, saying that upholding California's law would mark an expansion of federally regulated materials and could open the door to other restrictions by state legislatures.
"Aren't you asking this court to go where no court has gone before?" Appellate Judge Consuelo Callahan asked Morazzini.
"Is there anything out of limits for the Legislature to prohibit to minors?" Judge Alex Kozinski said. "What about games where people eat unhealthy foods and get fat?"
When asked by Judge Sidney Thomas about any differences between a violent video game and a violent book, Morazzini argued that the games are interactive and required a child to participate in the violence.
In a statement released after the hearing, State Sen. Leland Yee, a child psychologist who wrote the 2005 law, cited studies that show violent games can be linked to aggression, anti-social behavior and desensitization to violence.
Yee said he hoped the panel would "empower parents with the ultimate decision over whether or not their children play in a world of violence and murder."
But the video game industry argued that California failed to prove there is a connection between such games and psychological or other harm to children.
Smith also said video game manufacturers already have a voluntary rating system for their games and should not be required to label them. Kozinski questioned why the industry should not be forced to label video games, saying parents could still choose to buy whatever games they wanted for their children.
"I don't see why this is a big censorship thing," Kozinski said.
The appeals court is expected to make its ruling in the next few months. The case ultimately could be decided by the U.S. Supreme Court.