The U.S. Supreme Court should strike down bans on same-sex marriages, says a former Southern Arizona congressman.

Jim Kolbe, who was Republican representative in Southern Arizona from 1985 to his retirement in 2007, said he has signed on to a "friend of the court" brief urging it to strike down the U.S. Defense of Marriage Act when it considers California's Proposition 8, a ban on same-sex marriage.

"I signed on to this brief because I think it's my responsibility as a Republican, one who believes strongly in individual rights and individual liberties to stand up and say that the institution of marriage is one that should to be strengthened," said Kolbe, who is gay.

"We can strengthen it by making it possible for gay couples to have a committed relationship, to raise their children in a committed relationship," he said.

The Supreme Court later this month will hear arguments on California’s Proposition 8, which was passed by voters in 2008. Thirty-one other states, including Arizona, have constitutional or legal bans on same-sex marriage.

Kolbe called same-sex marriage a Republican issue, even if socially conservative people disagree.

“We as conservatives and Republicans want to strengthen the institution of marriage," he said. "So strengthening the institution of marriage means making that institution available to everybody. There’s no fact-based justification for different legal treatment for committed relationships between same-sex and different-sex couples.”