Australia's highest court has struck down a landmark law that allowed the country's first gay marriages.
Dozens have wed in the nation's capital, but those marriages will be annulled in light of Thursday's ruling, which found that the country's parliament - not state and territorial authorities - has the final say.
"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."
I don't want to be unmarried this afternoon.
Had the nation's top court upheld the Australian Capital Territory (ACT)'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.
The federal government had challenged the validity of the territorial law on the grounds that it conflicted with federal law.
The court decision means that the 27 couples who have wed since the ACT laws came into effect a month ago will have their marriages declared invalid.
"This is devastating for those couples who married this week and for their families," said Rodney Croome, national director of Australian Marriage Equality.
Ivan Hinton, who married his partner Chris Teoh in the capital Canberra, said outside court: "I don't want to be unmarried this afternoon."
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.
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.
Other countries where same-sex marriage is legal include Canada, Spain, Sweden and New Zealand.