Sydney (AFP) - Australia's High Court on Thursday struck down gay marriage in the nation's capital where dozens have wed under a landmark law, ruling that parliament must decide whether to approve same-sex unions.
Had the nation's top court upheld the Australian Capital Territory's gay marriage legislation it would have opened the door to similar laws being passed across the country, pressuring the government to make it legal at a national level.
In a unanimous decision, Australia's highest court ruled that the federal parliament -- not state and territory authorities -- had the ultimate say over marriage, and whether it was extended to same-sex couples was a matter for lawmakers.
"The Marriage Act does not now provide for the formation or recognition of marriage between same-sex couples," the court said.
"That Act is a comprehensive and exhaustive statement of the law of marriage," it added.
"Under the constitution and federal law as it now stands, whether same-sex marriage should be provided for by law is a matter for the federal parliament."
The decision means that the 27 couples who have wed since the ACT laws came into effect a month ago will have their marriages annulled as unconstitutional.
There were tearful scenes outside the court as those who had married digested the judgment, with Ivan Hinton describing it as "personally devastating" to have his vows to partner Chris Teoh overturned.
"In less than a week we've been married and we've been unmarried, at least on a legal level," he told reporters, fighting back tears.
"We're still married. I've made commitments to Chris to spend the rest of my life with him, through sickness and through health, in the good times and in the bad. Today's not particularly good."
Veteran gay rights campaigner Rodney Croome said the case represented major progress.
"Although there's been a defeat for marriage equality in the High Court today this week we've seen a much greater victory," an emotional Croome said.
"For the first time ever same-sex couples have married on Australian soil. That has been a huge step forward and one from which there is no return."
Instead of "protests or politics, or even laws and the constitution", Croome said the passage of the ACT laws had showed that gay marriage was about "love, commitment, family and fairness".
The ruling had also given campaigners a clear path forward, Croome said, putting the ball squarely in the parliament's court, and affirming "for the first time ever" that lawmakers "definitely" had the power to make same-sex marriage legal.
"Many people had assumed that until now but it has never been declared by the court," he said.
Others also took heart from the court's declaration that while the Marriage Act was restricted to male-female unions, the constitution did not inherently exclude same-sex couples from the definition of "marriage", underscoring that it was a political rather than legal issue.
Religious groups including the Australian Christian Lobby welcomed the ruling, saying gay marriage was irrelevant to most Australians and it was "time to move on".
Gay marriage has been explicitly outlawed in Australia since 2004, when then-prime minister John Howard amended the Marriage Act to specify that such unions were only valid between a man and a woman.
The conservative Tony Abbott-led government is opposed to gay marriage, despite Abbott's sister being a lesbian who is engaged and hopes to marry her partner.
Same-sex couples can have civil unions or register their relationships in most states across Australia but the government does not consider them married under national law.
For legal purposes they are considered de facto couples and have exactly the same rights as married couples.