A High Court ruling in favour of the ACT's same-sex marriage scheme may not bring political debate over the law to an end.

Lyle Shelton, managing director of the Australian Christian Lobby, said he was optimistic the court would overturn the marriage equality law.

Mr Shelton said if the court ruled the ACT law was found to be constitutional Australia would be left ''with a hodge-podge of marriage laws''. ''Now that is not in the nation's interest and something would need to be done to get us back to a state of uniform marriage laws,'' he said.

Mr Shelton did not specify what action should be taken to ensure uniformity of marriage laws.

The Federal Parliament has the power to overturn territory laws.

Mr Shelton said same-sex marriage bills had been rejected by the federal, NSW, South Australian and Tasmanian parliaments.

He said if the High Court struck down the ACT law, the same-sex marriage supporters should abandon the issue.

Rodney Croome, director of Australian Marriage Equality, said the High Court's ruling on the ACT law should be respected.

''If the ACT law is upheld then we call on the federal government and the Australian Christian Lobby to respect the independent umpire's call,'' Mr Croome said.

Marriage equality advocates turned their eyes on Wednesday to advancing marriage equality in the Federal Parliament.

Advocates have been in talks with Liberal, Labor and Greens MPs in the hope of establishing a cross-party working group, similar to that set up in the NSW parliament.

Greens senator Sarah Hanson-Young, who will introduce a marriage equality bill in this Parliament, has previously said she is open to members of other parties co-sponsoring the bill.

Australian Marriage Equality deputy director Ivan Hinton said cross-party co-operation had been crucial to achieving marriage equality in other countries such as New Zealand.

''There seems to be an enthusiasm to it,'' Mr Hinton said, after meeting with MPs on Wednesday.

Mr Croome said that even if the High Court overturned the ACT's law next week, the marriage equality movement in Australia had taken a significant leap forward.

''The weddings over the weekend will send a powerful message to our leaders and politicians that this is not about the law and politics but family and commitment and the love we all share,'' he said.