Minnesota became the twelfth US state to allow equal marriage, as Governor Mark Dayton on Tuesday signed a bill into law, allowing same-sex unions.

Mr Dayton signed the bill into law on Tuesday at 17:00 local time using eight separate pens. It will allow same-sex weddings to take place from 1 August.

Citing the US Constitution, Mr Dayton said: “The right to liberty certainly includes marrying the one you love.” Now that the bill has been signed, supporters plan to go to downtown St Paul, for a street party and celebratory concert.

Advocates of equal marriage have commended efforts in the state, which went from having a question on a ballot which would have banned equal marriage, to legalising it, in just over six months.

Yesterday’s vote in the Senate was 37 to 30, in which the Democrats hold a 39-28 majority. 

Minnesota for Marriage, an anti-equal marriage campaign group, has said it is mourning a “sad day” for the state, and that the measure will have “unintended consequences”.

Those opposed to the measure said during the debate in the Senate, leading up to the bill, attempted to use the argument that religious freedom was not protected said that it would be “unbearable” for religious organisations having to make a choice, said Senator Paul Gazelka.

Responding to Mr Gazelka, fellow Republican Senator Branden Petersen said he had mis-quoted information, and that the bill, and law as it stood before it was passed, protected religious organisations.

Other members of the US Senate suggested that the religious freedom amendment would allow businesses and organisations to discriminated based on race, as well as sexual orientation.

Ron Latz, asked “aren’t we passed that [kind of discrimination], as a society?”, referring to the amendment, which was defeated before the vote.

St Paul Mayor Chris Coleman, tweeted in favour of the measure passing in the house last week, and today that he had renamed the Wabasha Bridge in support of passing equal marriage.

Rainbow flags were also flown in St Paul, Minnesota ahead of the vote on equal marriage, in support of the measure.

The House of Representatives in the US state of Minnesota passed the bill to legalise equal marriage last Thursday, with a clear majority in favour.

Among the opposition was Republican Representative Peggy Scott, who said she was brought to tears by the prospect of same-sex couples being allowed to marry. 

Leading up to the vote, thousands of supporters and opponents of equal marriage gathered outside the House. During the debate, opponents to the measure argued that it was “not the time” for the measure, but its proponents denied they were “destroying” marriage, and said they were to “uphold it for all”.

In November 2012, Minnesotan voters avoided a constitutional ban on marriage equality, and pro-equality campaigners have since stepped up efforts to push for equal marriage to be legalised. 

A group opposed to equal marriage in the state has pledged half a million dollars to defeat any Republican legislator voting to legalise marriage equality.

On 6 November, voters in Minnesota voted ‘no’ on Amendment 1, a constitutional amendment that would have defined marriage as being a union solely between a man and a woman.