On Tuesday, India’s Supreme Court is set to give a ruling on petitions seeking to legalise same-sex marriage.

The petitioners say not being able to marry violates their constitutional rights and makes them “second-class citizens”.

The government and religious leaders have strongly opposed same-sex unions, saying they are against Indian culture.

If the court okays marriage equality, it will give India’s tens of millions of LGBTQ+ people the right to marry.

It would also set off momentous changes in Indian society as a lot of other laws, such as those governing adoption, divorce and inheritance, will have to be reimagined.

A five-judge constitution bench – which is set up to consider important questions of law – heard the case in April and May. Chief Justice DY Chandrachud, who is heading the bench, called it “a matter of seminal importance” and the deliberations were “livestreamed in public interest”. The court reserved its order on 12 May.

Justice Chandrachud had said they would not interfere with religious personal laws but look at whether a special law – that governs inter-caste and inter-faith marriages – could be amended to include LGBTQ+ people.

The court heard 21 petitions filed by same-sex couples – including some who are raising children together – LGBTQ+activists and organisations.

Lawyers for the petitioners have argued that marriage is a union of two people, not just a man and woman. They say that laws should be changed to reflect changing concepts of marriage over time and that same-sex couples also desire the respectability of marriage.

The Indian constitution, the petitioners have repeatedly insisted in court, gives all citizens the right to marry a person of their choice and prohibits discrimination on the basis of sexual orientation.

They point out that not being able to marry means they can’t hold joint bank accounts, co-own a house or adopt children together.

During the hearing, the judges appeared sympathetic to the concerns of same-sex couples and asked the government what it intended to do to address them.

The government began by questioning the court’s right to hear the matter at all, saying it was an issue that only parliament could decide.

Solicitor General Tushar Mehta, who represented the government, urged the top court to reject the petitions, saying that a marriage could take place only between a man and a woman who were heterosexual.

The authorities also criticised the same-sex petitioners, saying that they “merely reflect urban elitist views”.

In a rare show of unity, leaders from all of India’s main religions also opposed same-sex unions, with some insisting that marriage “is for procreation, not recreation”.

Disregarding the opposition from the government and religious leaders, the judges decided to take on the case.

They said they would not wade into religious personal laws but look at whether the Special Marriage Act (SMA) of 1954 could be tweaked to include LGBTQ+ people.

In India, an overwhelming majority of marriages are held under religious personal laws such as the Muslim Marriage Act and the Hindu Marriage Act.

But they recognise weddings only between couples from their religion or caste. So, earlier if a Hindu and a Muslim wanted to marry, one of them had to convert to the other’s religion.

“This was a very problematic concept,” says lawyer Akshat Bajpai, “as it defeated the concept of personal liberty – that includes the right to practise your religion – guaranteed by the Indian constitution.”

So, after independence, the government decided to bring in a legal mechanism for inter-faith or inter-caste marriages.

“The Special Marriage Act 1954, introduced by an act of parliament, de-hyphenated marriage with religion. It underlined that one wouldn’t have to abandon their religion in order to marry,” Mr Bajpai says. “This was a great step for personal liberty.”

In the court, the petitioners argued that replacing “man” and “woman” with “spouse” in the Act could do the trick and give them marriage equality.

But as the hearings progressed, it became clear that tweaking this one law may not be enough as there are dozens of laws that govern divorce, adoption, succession, maintenance and other related issues which mostly come under the ambit of religious personal laws.

“It’s an unprecedented situation. It requires the highest levels of statesmanship to craft this judgement,” says lawyer Akshat Bajpai.

It’s hard to second-guess what the judges would say in court, but one thing that is widely expected is that they would grant same-sex couples certain social and legal rights, such as allowing them to open joint bank accounts, nominate each other in their insurance policies and co-own property.

Solicitor General Mehta has also said in court that the government would be willing to look at giving same-sex couples these rights.

During the hearing, some of the judges spoke of “incremental changes”, saying sometimes they worked better for issues that concerned the wider society.

With the government vehemently opposing the petitions, Mr Bajpai says “the judges have to walk a tightrope” in a country where “marriage and family are at the heart of any religion”.

The top court’s judgement is being keenly awaited in a country which has around 140 million LGBTQ+ people according to globally accepted estimates.

Recent surveys have shown that acceptance of homosexuality has grown, especially since September 2018 when the Supreme Court decriminalised gay sex.

A Pew survey in 2020 had 37% people saying homosexuality should be accepted – an increase of 22% from 15% in 2014, the first time the question was asked in the country. And the latest Pew survey in June had 53% of Indian adults saying same-sex marriage should be legal, while only 43% opposed it.

But despite the change, attitudes to sex and sexuality remain largely conservative and activists say the community continues to face stigma and discrimination.

During the hearing, Mukul Rohatgi, one of the lawyers representing the petitioners, said society sometimes needed a nudge to accept LGBTQ+ people as equals under the constitution and if the top court legalised same-sex marriage, it would drive acceptance of the group.

BBC News India is now on YouTube. Click here to subscribe and watch our documentaries, explainers and features.