The High Court has struck down the ACT’s same-sex marriage laws.

The court unanimously ruled that the ACT’s Marriage Equality (Same Sex) Act 2013 could not operate concurrently with the federal Marriage Act 1961.

The ACT enacted its same-sex marriage legislation in November with the first couples marrying at the weekend.

About 30 couples have tied the knot.

In its decision, the High Court held that the federal parliament had power under the Australian Constitution to legislate for same-sex marriage.

As it now stood it was up to the federal parliament to make provisions for same-sex marriage.

The court said that federal legislation – which defines marriage as a union between a man and a women – was a comprehensive and exhaustive statement on the law of marriage.

It held that the ACT law aimed to provide for marriage equality for same-sex couples and not for some form of relationship different to that recognised under the federal marriage law.

As a result, the ACT could not operate concurrently with the federal Act.

The court held that the whole of the ACT Act was of no effect.

Supporters of gay marriage expressed dismay at the decision.

“This is devastating for those couples who married this week and for their families,” Australian Marriage Equality national director Rodney Croome said shortly after the decision was handed down in Canberra on Thursday.

However, he said the ruling was just “a temporary defeat”.

Australian Marriage Equality spokesman Ivan Hinton was one person who took advantage of the ACT laws, marrying his partner Chris Teoh in Canberra last weekend.

“I don’t want to be unmarried this afternoon,” he told reporters outside the High Court.

Western Australia state upper house MP Stephen Dawson, who married his partner in the early hours of Saturday in Canberra, said the court decision was disappointing.

“The fight for recognition goes on,” he tweeted.

ACT Attorney-General Simon Corbell urged the federal government to act following the “disappointing” decision.

“The prime minister should now allow a conscience vote on same-sex marriage in the federal parliament,” he said.