ACT Chief Minister Katy Gallagher says if same-sex laws fail in the High Court, it is up to the federal parliament to end discrimination.

ACT Chief Minister Katy Gallagher believes any High Court decision to strike down the territory’s same-sex marriage laws will force the federal parliament to act.

The court is scheduled to hand down its decision on a Commonwealth challenge to the laws at midday (AEDT) on Thursday.

Ms Gallagher admits she is anxious about the court’s ruling, especially as almost 30 same-sex couples have taken advantage of the laws by marrying in Canberra since Saturday.

But she defends her government’s decision to initiate the landmark legislation.

“Even if we are unsuccessful today, we think there has been a step forward in the marriage-equality debate,” she told ABC television.

If the laws are struck down, because they are inconsistent with the Commonwealth’s Marriage Act, the focus would shift to the federal parliament.

“We only introduced our bill when the federal parliament failed to end discrimination several months ago,” Ms Gallagher said.

Australian Greens senator Sarah Hanson-Young will introduce a private member’s bill on marriage equality to the Senate later on Thursday.