Defiant supporters of same-sex marriage are shifting their focus to the federal government after the High Court struck out the ACT's laws.
They are calling on Prime Minister Tony Abbott to allow a conscience vote in Federal Parliament.
The High Court overturned the country's first same-sex marriage laws, finding they could not operate alongside federal laws.
Marriage equality advocates were devastated by the decision, but said there had been a great victory on the path to marriage equality: the first same-sex marriages on Australian soil.
Australian Marriage Equality director Rodney Croome said the matter was now squarely at the feet of the Federal Parliament and marriage equality might have a fighting chance if Mr Abbott allowed his coalition colleagues a conscience vote on the subject.
ACT Chief Minister Katy Gallagher threw the challenge down to Mr Abbott.
"This is not a campaign he can avoid," Ms Gallagher said.
"Over to you, Mr Abbott".
The court ruled that the ACT law was inconsistent with the federal Marriage Act but found the federal parliament had power to legislate for same-sex marriage.
The Chief Minister called on the Coalition government to allow its MPs a conscience vote.
Ms Gallagher said the territory government was "unapologetic" for enacting its law and disappointed the court had not found in the ACT's favour after the "long hard road" that had been fought to end discrimination for same-sex couples in the ACT.
"We delivered on a commitment to the people of the ACT," she said.
"Thirty-one beautiful marriages happened."
Couples who married during the five-day window created while the judges were considering their decision were disappointed in the decision.
Darlene Cox, who married Liz Holcombe, said the ruling did not change how they felt about each other.
"And it doesn't change the fact that Saturday, for both of us, was one of the best days of our lives," she said.
"As far as we're concerned, we're married. We've done it."
Joel Player, who married Alan Wright in the moments after the law was enacted, was in tears.
Im proud of what me and the other couples have achieved, but mostly just I dont understand why they cant just see past it, that its about love and hope," he said.
We knew that we might have a broken heart today."
ACT Liberal leader Jeremy Hanson said the ACT government should never have attempted to introduce a local same-sex marriage scheme because marriage was a matter for the federal parliament.
Im not an advocate for same-sex marriage, Mr Hanson said.
We have had a consistent position that this is not constitutionally valid. This is not something that should be dealt with by the ACT Assembly.
Federal Attorney-General George Brandis welcomed the ruling that marriage was a matter for the federal Parliament.
The proceedings in the High Court have never been about the desirability or otherwise of same-sex marriage, he said.
The Government believes it is important that we have uniform marriage laws across Australia.
Federal Shadow Attorney-General Mark Dreyfus said Mr Abbott should allow Coalition MPs a conscience vote on the issue.
Importantly the High Court stated that marriage in the Australian Constitution includes a marriage between persons of the same sex," Mr Dreyfus said..
"This means that the Parliament can legislate for marriage equality."
Mr Dreyfus acknowledged the disappointment of the couples whose marriages were dissolved by the decision.
To all the couples who have married in Canberra over the past five days, you have made history.
"I commend you for the brave stand you have taken."
ACT Attorney-General Simon Corbell also called on Mr Abbott to allow a conscience vote on same-sex marriages in the Federal Parliament, as did ACT Greens MLA Shane Rattenbury.
"Today's ruling from the High Court was about legal technicalities it was not about the morality, the common sense or the human importance of ending marriage discrimination," Mr Rattenbury said.
"I believe that Tony Abbott will find himself on the wrong side of history if marriage equality is not secured at a Federal level this is an issue of civil rights for Australians, and in 20 years time, people will look back and wonder why anyone stood in the way of equality.
Meanwhile, the WA Greens introduced a federal marriage equality bill in WA Parliament on Thursday.
Greens leader Christine Milne said she was pleased the High Court had confirmed federal Parliament could legislate on gay marriage but she criticised the ACT's bill which was unanimously rejected.
''Regardless of what the court has decided, we will not give up until there is marriage equality in Australia,'' she said.
''What the court has decided has made it very clear that the federal parliament has the power to legislate for marriage equality.
Democratic Labor Party Senator John Madigan said any decision on the definition of marriage needed to be made by the people, not the courts or the parliament.
"I agree with the High Court's ruling on the ACT legislation - the Federal Marriage act clearly defines marriage as between one man and one woman,'' he said.
"The only way that this issue can be put to rest once and for all is by a referendum."
Australian Christian Lobby managing director Lyle Shelton described the judgment as a decision for common sense.
"What the ACT sought to do undermined [uniform national marriage laws]," Mr Shelton said.
Mr Shelton conceded the push for marriage equality would continue, but said he was concerned it would be "legislation by fatigue".
"A lot of parliamentary time at state and federal level has been used on the issue," he said.
"We've had somewhere in the order of 10 attempts in the past three years to legislate a new definition of marriage, either at state, territory or federal level.
Earlier outside the High Court, anti-gay marriage activists waved banners and chanted "God is love", while singing hymns before the crowd.
They called for more public consultation on the subject, "its impact on families and the biological family unit".
They criticised the ACT government for not canvassing views within the Canberra community before passing the law in October.
The Human Rights Law Centre's Anna Brown said the decision at least pointed to a way forward.
"This is obviously a blow to the same-sex couples who have made the most of the short window of opportunity to get married in the ACT," she said.
"Fortunately, there is a silver lining the High Court has confirmed beyond doubt that the Australian Constitution allows the Federal Parliament to legislate for marriage equality,"