The High Court will hold a directions hearing on the Commonwealth's challenge to ACT same-sex marriage laws on Friday.
The Commonwealth lodged its objection to the laws on Wednesday, a day after they passed the ACT Legislative Assembly.
It wants an expedited hearing so a decision can be made before the first marriages happen in early December.
The Commonwealth argues the ACT law is inconsistent with the federal Marriage Act and Family Law Act.
But the ACT government says it has created a separate form of marriage for same sex couples capable of operating in parallel with the federal laws.