Saying trans women are not real women is a belief that "must be tolerated", a judge has ruled as he overturned the decision of an employment tribunal.
Maya Forstater, 45, had argued that she had been discriminated against on the basis of her beliefs when she lost her job as a tax expert over a series of tweets questioning government proposals to allow people to self-identify as the opposite sex.
An employment tribunal had ruled that her "gender critical" belief that someone cannot change their sex was so offensive to trans people that it could not be protected under the Equality Act or freedom of speech laws.
That decision was overturned at the Employment Appeals Tribunal on Thursday as Mr Justice Choudhury, sitting with a panel, ruled that they "may well be profoundly offensive and even distressing to many others, but they are beliefs that are and must be tolerated in a pluralist society".
She won the appeal after the Equality and Human Rights Commission intervened to back her legal argument.
The judgment noted that "although many might disagree with the proposition that sex is binary and that gender identity is a social construct, that is what the law of the land currently states".
Mr Justice Choudhury said that the right to freedom of speech applied to the expression of views that might "offend, shock or disturb".
But he stressed that his tribunal was not making a judgement on the merits of the trans debate and "does not mean that those with gender-critical beliefs can 'misgender' trans persons with impunity" as that could amount to harassment or discrimination.
Co-workers complained about ‘transphobic’ messages
Ms Forstater was working at the Centre for Global Development (CGDE) in 2019 when she published messages on her personal Twitter account, including the statement that male people were not women.
It led to complaints from her colleagues who said that the statements were "transphobic" and as a result her visiting fellowship was not renewed and she was offered no more consultancy work.
She lodged a claim for direct discrimination as a result of her "gender critical" belief that "sex is biologically immutable" that "men are adult males" and "women are adult females".
She lost that argument - seen as a test case - in December 2019, with an employment judge ruling that there was no legal right to question whether a trans-gender person is a man or a woman.
The panel had concluded that her belief had not passed the test of "being worthy of respect in a democratic society" –in the same way as Nazism or totalitarianism.
However, Mr Justice Choudhury said they had "erred in law" as her "widely shared" beliefs which "did not seek to destroy the rights of trans persons, clearly did not fall into that category".
The matter will now be sent back to a tribunal to decide whether she lost her job because of that belief.
Ms Forstater, co-founder of campaign group Sex Matters, said she was "delighted to have been vindicated".
She said: "Being a woman is a material reality. It is not a costume or a feeling. Institutions that pretend sex doesn’t matter become hostile places for women, in particular.
"After this judgment, employers and service-providers that ignore sex and silence women who object, need to consider whether they are acting unlawfully, and the substantial legal risks they face if they do not change their approach."
Amanda Glassman, chief executive officer of CGDE, said that the decision was "disappointing and surprising" and was a "step backwards for inclusivity and equality for all".
"We're currently considering the various paths forward with our lawyers," she added.