Australia’s highest court struck down a landmark law Thursday that had begun allowing the country’s first gay marriages, shattering the dreams of more than two dozen same-sex newlyweds.

The federal government had challenged the validity of the Australian Capital Territory’s law that had allowed gay marriages in the nation’s capital, Canberra, and its surrounding area starting last Saturday.

The High Court unanimously ruled that the ACT’s law, passed in October, could not operate concurrently with the federal Marriage Act, which was amended in 2004 to define marriage as between a man and a woman.

Prime Minister Tony Abbott opposes gay marriage, and his coalition blocked two federal bills last year that would have allowed legal recognition of same-sex partnerships.