California’s ban on same-sex marriage is unconstitutional, serves no legitimate purpose and should be overturned, a San Francisco judge ruled this week.

In his ruling on Monday, which is certain to be appealed, Superior Court Judge Richard Kramer said no rational purpose exists for limiting marriage in this state to opposite-sex partners.

He said the state’s historical definition of marriage could not justify the denial of equal protection for gays and lesbians.

Simply put, same-sex marriage cannot be prohibited solely because California has always done so before, he said.

If the ruling is upheld, California will become only the second state in the US after Massachusetts to legalise same-sex marriage.

Opponents are already mobilising.

California attorney general Bill Lockyer is expected to file a notice of appeal with the California Supreme Court before the end of this week, and two legal groups representing religious conservatives have also vowed to appeal.

To rule that there is no rational purpose to preserve marriage as the union of one man and one woman is ludicrous, Matthew D Staver of the Campaign for California Families said.

Both sides of the debate agree the ruling could spur politicians on to amend the state constitution to ban same-sex marriage.

Yet on Monday California Governor Arnold Schwarzenegger said while he didn’t believe in gay marriage, he didn’t favour amending the constitution to force a ban. He said he would support whatever decision the Supreme Court made.

The City of San Francisco and several of the 4,000 same-sex couples who married in San Francisco took the matter to court.

The couples received marriage licences from Mayor Gavin Newsom that were annulled after four weeks, when the California Supreme Court ruled against Newsom’s authority.

After Lockyer’s ruling was announced this week, Newsom was joined at a news conference by several of the gay and lesbian couples involved in the suit.

I am so happy that my parents can finally get married, said Ericka Sokolower-Shain, the 15-year-old daughter of plaintiffs Karen Shain and Jody Sokolower said.

My parents have been together for over 30 years. They have been together so long they can practically read each others’ minds. It is only right they should be able to get married.

We are overjoyed by today’s ruling, Stuart Gaffney and John Lewis, two other plaintiffs in the lawsuit said.

Fifty years ago, the California courts paved the way for my mum and dad to get married when they struck down the state law barring interracial couples from marriage, Gaffney added.

© Star Observer 2017 | For the latest in lesbian, gay, bisexual, trans* and intersex (LGBTI) news in Australia, be sure to visit starobserver.com.au daily. You can also read our latest magazines or Join us on our Facebook page and Twitter feed.