Rebecca Steinfeld described the ruling as a "step closer to opening civil partnerships to all"
A heterosexual couple has won a legal bid at the UK's highest court for the right to have a civil partnership instead of marriage.
Rebecca Steinfeld, 37, and Charles Keidan, 41, had been prevented from having the legal union because a UK bill says only same-sex couples are eligible.
The couple, who have two young daughters, claim the government's position was "incompatible with equality law" and the Supreme Court in London has now ruled they are being discriminated against.
The academics, from west London, have "deep-rooted and genuine ideological objections to marriage" and were "not alone" in their views, according to their lawyer.
Barrister Karon Monaghan QC said matrimony was "historically heteronormative and patriarchal" and the couple's objections were "not frivolous".
Since March 2014, same-sex couples in the UK can choose whether to enter a civil partnership or to marry.
However, this has not been possible for different sex couples - which led Ms Steinfeld and Mr Keidan to claim the law was discriminatory.
On Wednesday, five justices at the Supreme Court, who heard the couple's case in May, ruled the ban was "incompatible" with human rights laws.
Outside court, Ms Steinfeld told reporters: "Today we are a step closer to opening civil partnerships to all, a measure that would be fair, popular and good for families and children across the country.
"We are elated. But to get this far we have had to go toe-to-toe with the government over four long years."
Mr Keidan said there was now only one option - "to extend civil partnerships to all".
He said it was hoped the British government will "act with urgency" for the sake of thousands of couples.
The decision overturns a previous ruling at the Court of Appeal last February.
In 2017, the three judges hearing the case accepted there had been a breach of the couple's human rights, but said the government should be allowed more time to decide on the future of civil partnerships.