The debate over same-sex marriage in Australia will reach a critical juncture on Thursday when the High Court hands down its findings in the Commonwealth's case against the ACT government.
Victory for the ACT could see similar laws enacted by other state parliaments, while a loss could send the ACT back to the drawing board or even preclude state and territory governments from passing state-based laws for same-sex marriage.
The High Court will deliver its findings at midday, less than 24 hours after the final marriages took place in the five-day window granted to the ACT before the ruling in the landmark case.
A federal bill for marriage equality is scheduled to be introduced into the Senate by Greens Senator Sarah Hanson-Young on Thursday.
Senator Hanson-Young, Liberal Senator Sue Boyce and Labor Senator Louise Pratt announced a cross-party working group on Wednesday to advance national reform of marriage laws.
At least 27 couples have married in the ACT since Saturday, despite the possibility that the territory law - and their marriages - could be struck down on Thursday.
The ACT government has vowed to battle on if it loses the case, but that will depend on whether the High Court's ruling leaves the door open to another attempt at legislating.
''If they rule that the Commonwealth's covered the field, then really the issue goes squarely to the Federal Parliament,'' Chief Minister Katy Gallagher said.
Whatever the verdict, Ms Gallagher said Thursday would mark a crucial turning point in the debate about marriage equality in Australia, and the case had fixed the issue squarely on the national agenda.
Sydney residents Annette Cairnduff and Kylie Gwynne were among the final couples to marry in Canberra on Wednesday.
Before their two sons, relatives and friends, the pair exchanged vows and said their ''love and ordinariness'' were what Australians needed to see.
''I think a week of love stories - even if it's only a week - will make a difference to some kid out there,'' Ms Gwynne said.
''It doesn't matter what happens [on Thursday] because we've had this joyous event today where people have heard us publicly express feelings they wouldn't hear us say to each other every day''.
Their 14-year-old son Patrick spoke to the crowd of his pride in seeing his parents' relationship ''publicly acknowledged after all the love they have given my brother and me''.
Thursday's High Court finding will determine whether the ACT law is inconsistent with federal marriage laws and whether the federal parliament has sole powers when it comes to marriage.
Constitutional law expert George Williams said both sides had put good arguments to the court.
Professor Williams said the six-member bench in the case could play a role if the result was split three-three.
If it is a three-three split the Chief Justice gets a casting vote.
''I think you predict the High Court at your peril,'' Professor Williams said.
''The decision itself will determine the gay marriage debate in Australia. It's a critical turning point.''
Morning & Afternoon Newsletter