Section 377 is “an archaic, repressive and unjust law that infringed on basic human rights”.

India’s highest court, the Supreme Court, has upheld a colonial-era law, known as Section 377, which criminalises gay sex, throwing out a 2009 New Delhi High Court decision that ruled the law was unconstitutional.

The New Delhi ruling had effectively de-criminalised gay sex between consenting adults in private.

This change could see gay people once more jailed for up to ten years.

The Supreme Court is known for its broadly progressive judgments that often order politicians or officials to respect the rights of the poor, disadvantaged or marginalised communities.

And, as the Guardian reported, few people expected that a legal challenge – launched by conservatives including Muslim and Christian religious associations, a right-wing politician and a retired government official-turned astrologist – against the 2009 decision on Section 377 to succeed.

Anjali Gopalan, activist and director of the Naz Foundation Trust, the Indian HIV campaign group which initially lead this phase of the movement to repeal Section 377 and took the issue to the Delhi High Court, told the Guardian she had been “horrified by the judgment”.

“It reflects a conservative mindset. After so much effort we are back to square one. Whatever we have gained over the years we seem to have lost.”

The Foundation has said that it will file a petition seeking a review of the Supreme Court’s ruling.

The decision, made on World Human Rights Day, makes India the 42nd Commonwealth nation in which same-sex activity illegal. 

Dr Purna Sen, former head of human rights at the Commonwealth Secretariat and chair of the Kaleidoscope Trust, a UK based charity working to uphold the human rights of lesbian, gay, bisexual and trans people internationally, condemned the decision.

Dr Sen said: “The Supreme Court’s ruling is a terrible setback for the struggle to secure equal rights for LGBT people, not just in India, but in many of the Commonwealth countries that still enforce colonial era restrictions on the liberties of LGBT people.”

Dr Sen, who was born in India and now works at the LSE in London, added: “The 2009 ruling that read the ban on same-sex relationships as being at odds with the Constitution acted as a real beacon for hope in the Commonwealth.”

“Today’s ruling, sadly, is a setback for India and sets a worrying precedent.”

The Supreme Court took the view that a section of the Indian penal code dating back to the nineteenth century that outlawed sexual acts ‘against the order of nature’ took precedence over the right to equality.

It is now up to the Indian Parliament to legislate on this issue, according to Justice GS Singhvi, the head of the Supreme Court bench.

But Sonia Gandhi, the president of the ruling Congress party has called on the national assembly “to address this issue” and described Section 377 as “an archaic, repressive and unjust law that infringed on basic human rights”.

And law minister Kapil Sibal said the government has not abandoned efforts to make homosexuality legal, and that the country must take swift action to challenge the Supreme Court decision.

Navi Pillay, the United Nations’ high commissioner on human rights, described the high court’s move as a ‘significant step backwards’ as the UN called on the Indian government to seek a rapid review of the decision.

In a statement issued in Geneva, Pillay said, “Criminalising private, consensual same-sex sexual conduct violates the rights to privacy and to non-discrimination enshrined in the International Covenant on Civil and Political Rights, which,” she pointed out, “India has ratified.”

And Dr Sen told PinkNews, “when the Delhi High Court made its announcement in 2009, we all got excited and thought gay sex had been decriminalised.

“Also, many believed that it was a fantastic judgement which interpreted the provisions of the Indian constitution”.

“We need to not lose heart but to keep mobilising and keep fighting”.