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They are currently prevented from having a legal union through the route of civil partnership because the Civil Partnership Act 2004 says only same-sex couples are eligible. The academics, who live in Hammersmith, west London, suffered defeat at the Court of Appeal in February last year, but were given the go-ahead in August for a Supreme Court hearing. The panel of Supreme Court justices, including the court's president, Lady Hale, heard the couple's case in May and announced their decision on Wednesday. The judges granted a declaration that the 2004 Act was "incompatible" with human rights laws on discrimination and right to a private and family life.

Five Supreme Court justices unanimously allowed an appeal by Rebecca Seinfeld and Charles Keidan

Lord Kerr, announcing the court's decision, said the Government "does not seek to justify the difference in treatment between same-sex and different sex couples". He added: ”To the contrary, it accepts that the difference cannot be justified." What the Government sought was "tolerance of the discrimination while it sorts out how to deal with it". He concluded: "That cannot be characterised as a legitimate aim."

Lord Kerr said it was "salutary to recall that a declaration of incompatibility does not oblige the Government or Parliament to do anything". The couple, who have two daughters aged nine months and two, claimed the Government's position is "incompatible with equality law". During the hearing, their barrister, Karon Monaghan QC, told the court they have "deep-rooted and genuine ideological objections to marriage" and are "not alone" in their views. She said matrimony was "historically heteronormative and patriarchal" and the couple's objections were "not frivolous".

Charles Keidan (R) and Rebecca Steinfeld (L) leave the Royal Courts of Justice

Ms Monaghan added: "These are important issues, no small matters, and they are serious for my clients because they cannot marry conformable with their conscience and that should weigh very heavily indeed." The Court of Appeal agreed that the couple had established a potential violation of Article 14 of the European Convention on Human Rights, which relates to discrimination, taken with Article 8, which refers to respect for private and family life. But, by a majority of two to one, the judges said the interference was justified by the Government's policy of "wait and evaluate". The Government said it was decided, after public consultations and debate in Parliament, not to extend civil partnerships to opposite-sex couples, abolish them or phase them out at that stage. The aim was to see how extending marriage to same-sex couples impacted on civil partnerships before making a final decision which, if reversed in a few years' time, would be disruptive, unnecessary and extremely expensive.

Charles Keidan and Rebecca Steinfeld pose with placards outside the Royal Courts of Justice

Rhiannon Lloyd, Barrister at 4PB, said: “Whether straight couples should be able to access a civil partnership reserved only for same sex couples has been a divisive topic. Today the Supreme Court ruling in this case marks a stunning victory for those who feel marriage is a patriarchal and out dated means of marking a relationship. “Though this judgment does not compel the government to change the law, the government conceded that the legislation was discriminatory under article 14 of the ECHR but argued that was justified while it tried to sort out what do about it. “The Supreme Court rejected this as a legitimate justification saying that to create a situation of inequality and then ask for time for that inequality to be cured, in this case several years, is less deserving of a margin of discretion. Many will see this as a victory for those campaigning for the equal treatment of straight and same sex couples, some will also argue that this represents a victory for women’s rights.” James Carroll, Partner at Russell-Cooke, said: “Today’s decision is a victory for common sense - the denial of civil partnerships to unmarried couples is undoubtedly unfair and discriminatory. This wasn’t intentional. It comes about due to the manner in which civil partnerships were first introduced in 2005.

Charles Keidan and Rebecca Steinfeld address the media

“At the time, while many thought they may be a stepping stone to same-sex marriage, the position was far from certain and it gave same sex couple the ability to formalise, register and regulate their relationships in a form which was almost identical to marriage but didn’t bear the name. “Seven years on same sex marriage was introduced, and we became the first country to openly discriminate against opposite sex couple who were denied the choice between civil partnerships and marriage. For whatever personal reasons some people do not want to marry, but want their relationship to be registered and regulated. “In the same way that any such rights were denied to gay people before the civil partnership act, it seems completely contrary to the principle of equality that heterosexual couples were denied the same choice. This is nothing to do with undermining marriage, it is about equality before the law, regardless of sexuality.”