The case involves seven same-sex couples who sued the state, saying it is violating its own constitution by denying them the right to marry.
"How do plaintiffs answer their children's questions about why they are not married?" asked attorney David Buckell, arguing for the couples. "The only answer is that the state does not think their relationships are worthy."
Conservative groups filed documents contending that allowing same-sex marriage would harm society. The state did not make that argument in defending its ban, but said allowing same-sex marriage is an issue for legislators, not judges.
"To allow same-sex couples to marry would not be removing a barrier to marriage, but redefining marriage itself," Deputy Attorney General Patrick DeAlmeida told the court.
DeAlmeida fielded the brunt of the judges' questions in the hour-long hearing, including what might be protected by preventing same-sex marriage in New Jersey, one of 16 states where it is specifically illegal to discriminate based on sexual orientation. The state also has no legal barriers for same-sex couples to adopt children and recognizes domestic partnerships, though those do not offer all the legal protections of marriage.
"The Legislature has an interest in protecting the institution of marriage," DeAlmeida said.
Chief Justice Deborah T. Poritz responded: "It's not as if the institution of marriage hasn't changed in rather dramatic ways."
When asked about polygamy, Buckell said that marrying multiple partners is a different subject because it would introduce new issues, such as how divorce would work.
"You seem to be arguing that because it's complicated with polygamy" there's a legal difference, Poritz said, cautioning the lawyer to tread gingerly with that contention.