SAN FRANCISCO » A federal appeals court in San Francisco waded again into the debate over the constitutionality of gay marriage, with attorneys for both sides arguing over whether legalizing it would harm children.

The three judges on the 9th Circuit Court of Appeals — two of whom have ruled in previous cases in favor of gay rights — reserved many of their most pointed questions at the defenders of state bans in Idaho, Nevada and Hawaii.

Judge Marsha Berzon appeared critical of the attorney defending two of the bans, saying he was sending a message that families headed by same-sex couples were "second-rate."

"You’re sending a message that these are less desirable families" she said. "That is what you’re doing. That is what you say you’re doing."

The hearing is the first time since it declared California’s gay marriage ban unconstitutional that the 9th Circuit is listening to arguments over same-sex weddings in a political and legal climate that’s vastly different than when it overturned Proposition 8 in 2012. State and federal court judges have been striking down bans in more than a dozen states at a rapid rate since a landmark U.S. Supreme Court ruling last year.

Attorney Monte Neil Stewart faced tough questions from Berzon as he defended Idaho’s ban.

Stewart told the panel that same-sex marriage would undermine children’s right to be raised by a father and mother. Same-sex marriage would undercut the message that a man who fathers a child should get in a relationship with the female mother, he said.

"This is a contest between two different messages," Stewart said. "The message of man-woman marriage is: ‘Men, you’re valuable and important in the upbringing of the children you bring into this world. Women, you are valuable and important in the upbringing of children you bring into this world.’ Genderless marriage does not send that message, indeed it undermines it."

Berzon questioned how gay marriage differed from the current model of marriage, which she called "genderless." Berzon said that with gay marriages occurring, "the train has already left the station."

Deborah Ferguson, an attorney representing gay marriage supporters opposed to Idaho’s ban, said children of same-sex couples don’t have the same protections as children of heterosexual couples.

"(They) don’t have two legal parents to protect them," she said. "That is sending a powerful message. That tells those children that their parents’ marriages aren’t worthy of respect. That’s a very harsh message."

The 9th Circuit heard arguments about Nevada and Hawaii’s gay marriage ban as well.

Attorney Tara Borelli said Nevada’s gay marriage ban sends a message to same-sex couples that they and their families are inferior. The ban is particularly damaging to children and humiliates them, Borelli said.

Stewart argued in favor the Nevada ban in part on the basis that states had the right to make choices about gay marriage.

Advocates of gay marriage in Hawaii have urged a federal appeals court to dismiss a case filed by same-sex couples, saying it was now moot because the state legislature had approved gay marriages.

Clyde Wadsworth, who represents gay couples, told the judges that the original parties to the case now agree they no longer have any disputes.

But Kenneth Connelly, of the Hawaii Family Forum, said the issues in the case could still resurface if the Hawaii Supreme Court strikes down the state’s same-sex marriage law.

University of California, Irvine law professor Douglas NeJaime said "this (9th Circuit) panel seemed very skeptical of the arguments in favor of the bans."

NeJaime and many others, including 9th Circuit Judge Stephen Reinhardt, said the issue of gay marriage will ultimately be decided by the U.S. Supreme Court.

Outside court, gay couples who filed lawsuits in Nevada and Hawaii expressed optimism that the court would strike down their states’ marriage bans.

"We have been waiting a long time to marry," said Beverly Sevick, who attended the hearing with Mary Baranovich her partner of 43 years. Two of the couples’ three children attended the hearing as well and rejected arguments that same-sex parents couldn’t provide stable parenting.

"We were a stable home," said Susan Crain, the couple’s 51-year-old daughter. "We got grounded like everyone else."

The 9th Circuit in 2012 invalidated Proposition 8 because it singled out a minority group for disparate treatment for no compelling reason. The U.S. Supreme Court dismissed the case last year without ruling on the legal merits of gay marriage.

The case for gay marriage was bolstered when the court earlier this week unveiled the names of the three judges assigned to decide the issue in those three states. Judges Berzon and Ronald Gould were appointed by President Bill Clinton. And Reinhardt, appointed by President Jimmy Carter, is considered one of the most politically liberal jurists on the 29-judge court. Reinhardt wrote the 2012 opinion striking down California’s gay marriage ban.

The 9th Circuit panel is under no deadline to rule.

Associated Press writer Sudhin Thanawala contributed to this report.