Ireland’s President has signed the country’s same-sex marriage amendment into law.

President Michael Higgins signed the amendment into law on Saturday, following a referendum in May at which equal marriage was approved.

Now that the law has been signed, legislation can now be brought forward to enact same-sex marriage.

In doing so, Ireland will become the first to legalise equal marriage based on a popular vote, as a referendum was required to move constitutional change.

The legislation is expected to be brought forward in September, and the first marriages could take place later this year.

Following the landslide victory in May, Irish justice minister Frances Fitzgerald promised to implement the law as soon as possible, saying: “I am very conscious that many couples will want to get married as soon as possible. I am working to make that happen.

“My intention is to seek Government approval for the Marriage Bill 2015 in June with the aim of introducing the Bill into the Oireachtas immediately thereafter so that the legislation can be enacted before the summer recess.”

However, amid likely-pointless legal action from opponents over the result of the referendum, the Irish Times previously reported that the first weddings could be pushed back until 2016.

A government source told the newspaper: “Our hands are tied. We are at the mercy of the courts.

“We are ready to go when the referendum result is final but it looks like we are a long way from that point.

“Best-case scenario, we can have the legislation enacted by the end of July. Worst-case scenario, we could be talking potentially months of delay.”