First gay union was organised in Australia by two "delighted" men who became Australia's first same-sex couple to hold a legally recognised civil partnership ceremony.
Warren McGaw and Chris Rumble said they were honoured to celebrate their union in the Rose Garden of Old Parliament House in Canberra, 20 years after beginning their relationship.
"We thought we'd take this opportunity not only for gay couples Australia wide ... but just for human rights," McGaw said.
"I think the majority of Australians are behind us."
The national government, however, is seeking legal advice on whether to quash the laws, passed this month in the Australian Capital Territory (ACT) parliament, allowing same-sex couples a legally recognised union.
"The reality is there are a number of people in the community who feel strongly about this issue both ways," said Attorney-General Robert McClelland.
McClelland, of the ruling centre-left Labor party, overturned a similar bid in February 2008 on the grounds it broke national laws on marriage, which is defined as between a man and woman.
It was the second time the national government had overturned gay marriage legislation in the ACT, after an earlier attempt was halted in 2006.
"I would like to resolve the matter with the minimum amount of angst, a minimum amount of trauma, and the minimum amount of time," said McClelland.
McGaw and Rumble said they would be "devastated" if the law was thrown out, despite assurances that any unions already celebrated would stand.
"We'll be really disappointed and devastated if (the legislation) does get overturned," said McGaw.
"But we took the opportunity today to have the legal ceremony as the law stands today."
"We couldn't be happier, couldn't be more delighted."
The ruling party voted in August to uphold Australia's gay marriage ban, but the government has also passed legislation to remove same-sex discrimination from almost 100 national laws including areas such as tax and employment.