Gender equality activist Norrie has been campaigning for recognition of a "gender neutral" sex YouTube

Australia's highest court has ruled that a person can be legally recognised as gender neutral, as opposed to male or female.

Ending a long legal battle by a sexual equality campaigner, the high court dismissed a New South Wales state appeal to recognise only men or women. In a unanimous judgement, the court said that it "recognises that a person may be neither male nor female, and so permits the registration of a person's sex as 'non-specific'."

The decision revolved around Norrie, a 53-year-old Scottish-born activist who had been campaigning for recognition of a new, non-traditional gender.

Norrie, who only goes by a single name, was born male but underwent gender reassignment surgery in 1989 to become a woman. But the surgery failed to resolve Norrie's ambiguity about sexual identity.

The Sydney-based campaigner said: "I'm overjoyed. It's been a long time from start to end but this has been a great outcome. Maybe people will understand now that there's more options than just the binary."

Norrie made headlines in February 2010 when an application to the New South Wales Department of Births, Deaths and Marriages accepted that "sex non-specific" could be accepted for Norrie's records. Shortly afterwards, however, the office revoked its decision.

The move, which Norrie described as "socially assassination", led to a series of appeals which resulted in the NSW Court of Appeal recognising Norrie as gender neutral in 2013.

Norrie's lawyers argued that the activist was being forced to "live a lie" each time their client filled in a document that only listed two options for gender.

The Human Rights Law Centre, which provided testimony in Norrie's case, said the court had "rejected outdated notions of gender".

Anna Brown, the centre's litigation expert, told AFP: "Sex and gender diverse people face problems every day accessing services and facilities that most Australians can use without thinking twice."

She said that although the decision did not mean people could simply identify themselves as "non-specific" and expect legal recognition, it was essential that legal systems "accurately reflect and accommodate the reality of sex and gender diversity that exists in our society".

Under the law, only a person who has undergone gender reassignment surgery could nominate themselves as "non-specific" after presenting medical evidence. Brown added that is is yet unclear who gender-neutral people would be able to marry.