Australia’s highest court has overturned a landmark law which had begun allowing the country’s first gay marriages.

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

It means at least 27 weddings have been deemed invalid.

The federal government’s lawyer argued that having different marriage laws in various Australian states and territories would create confusion.

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

Gay marriage has legal recognition in 18 countries as well as 16 U.S. states plus the District of Columbia.