The Australian Capital Territory (ACT) has become Australia’s first state to introduce marriage rights for same-sex couples.

On Tuesday its Parliament passed the law in a 9-8 vote, drawing a standing ovation from the 200-strong crowd in the public gallery. Many sang John Paul Young’s 1970s pop hit Love Is In The Air in celebration.

Same-sex couples are expected to rush to Canberra, the national capital, to tie the knot before the Federal Government can overturn the law.

The first same-sex weddings in the ACT could take place by December.

Despite having a gay siblingAustralia’s Prime Minister Tony Abbott continues to oppose equal marriage and has supported efforts to halt the ACT’s equal marriage bill in the courts.

Last week, Mr Abbott said that the ACT court challenge was about upholding the Australian constitution and about preserving a “uniform approach throughout the commonwealth” to marriage laws.

Yesterday, several amendments were made to the ACT’s bill in order to safeguard its legal passage. 

Same-sex couples living in the ACT have been allowed to register their partnerships since 2008 and hold civil partnership ceremonies since 2009, when the ACT became the first territory in Australia to introduce such legislation.

Rodney Croome, national director of Australian Marriage Equality, said at least 500 Australian gay couples from outside Canberra want to marry there as soon as possible. Only about 360,000 of Australia’s 23 million people live in the ACT.

Mr Croome described any federal intervention to prevent the marriages as cruel.

“It’s cruel of the Federal Government to try to undo solemn vows of lifelong commitment made by the couples who will marry under this law,” he said.

“Those vows bring great joy to those couples and their families and do no-one any harm. Why would anyone want to undo them?” he added.

Australian federal law was amended in 2004 to specify that marriage can only be between a man and a woman. But it also specifically applied to heterosexual couples, and some lawyers argue that leaves states free to legislate for same-sex marriage.

Equal marriage remains banned at a federal level in Australia and efforts to legalise the measure failed in the Australian Parliament in September 2012.

But Tony Abbott has suggested there is nothing to stop the Federal Parliament from reconsidering the issue.

However, it is unclear whether the absolute parliamentary numbers are there for a change in the law, even if Mr Abbott grants his MPs a conscience vote.

Christine Forster, the sister of Mr Abbott, has revealed that she has proposed to her partner Virginia Edwards.