Although three of the 15 justices said this clause similarly violates the constitution, the Supreme Court requested a high court to look at it again.

In general, a person born a woman can have their genitals appear male through hormone therapy, but for a man to have female-looking genitalia, surgery is almost always needed.

“For people seeking to change from a man to a woman, the latest decision has no benefits,” said Marina Kurashina, vice-head of the General Incorporated Association Japan People with Gender Identity Disorder.

The clause is in focus as conservative members of the ruling Liberal Democratic Party have raised concerns that eliminating the requirement on genital resemblance could cause social disruption, citing the examples of transgender people entering sex-segregated spaces such as bathrooms and traditional public baths.

One LDP lawmaker angrily called the Supreme Court’s decision “unbelievable” while another said it would “obviously cause social confusion”.

When Japan enacted a law to promote understanding of sexual minorities in June, conservative LDP lawmakers launched a parliamentarians’ group to protect the “safety and security of all women” and ensure “fairness in women’s sports”.

Even before the top court reached the decision on Wednesday, the group’s co-leader, LDP lawmaker Eriko Yamatani, in September asked Ken Saito, the justice minister at the time, to maintain the current legal requirements for gender change.

Among civic groups, Midori Miyama, 61, a member of a coalition of groups seeking to protect women’s spaces, said: “It is an abnormal decision. I must say that the judiciary made a reckless move at a time when the public discussion has not matured.”

Born as a man, Miyama has undergone surgery to become a woman.

She said transgender women like herself who have undergone surgery “have gained trust from women and have been accepted by society by removing male genitals”, adding that the high court re-examining the clause on genital resemblance “should decide to maintain it”.

“Women are afraid and angry that when the requirements are eased, they could be exploited,” Miyama said.

Taro Takimoto, a lawyer for the coalition, criticised the top court’s decision, saying: “Its logic is based on the idea that gender identity should be prioritised over the rights of others.”

The historic decision came as Japan slowly moves to implement policies to protect the rights of sexual minorities.

The legislation to promote understanding of sexual minorities was enacted following intense debate between the ruling and opposition parties. The country previously had no law prohibiting discrimination against LGBT individuals.

In the absence of legal recognition of same-sex partnerships in Japan, some local governments have taken steps to recognise same-sex partnerships, such as issuing certificates, which are not legally binding but help same-sex couples apply for municipal housing, among other benefits.

Pressure from the courts to do more has also mounted, with some recently ruling the non-recognition of same-sex marriage to be unconstitutional or “in a state of unconstitutionality” – with the latter term indicating that the court would rule it unconstitutional if legislative action is not taken in a reasonable period.

In a unanimous decision, the top court has also ruled against the trade ministry’s imposition of restrictions on the use of women’s restrooms by a transgender official.

“In recent years, the partnership system [for same-sex couples] has expanded rapidly,” said Justice Mamoru Miura in his opinion attached to Wednesday’s decision, stressing the change in the social environment towards sexual minorities.

While the clauses effectively requiring surgery in switching gender on a family registry were not hot-button issues when the law containing them was debated in 2003, the mood changed after the World Health Organization in 2014 called for the elimination of forced and involuntary sterilisation, sending shock waves through the community of health and medical specialists in the country.

According to the Hamamatsu branch of the Shizuoka Family Court that ruled the surgical requirement unconstitutional earlier this month, of around 50 countries that allow gender change by law, 40 do not require the removal of reproductive capacity.

03:01

Tokyo issues same-sex ‘partnership certificates’ amid cheers from LGBTQ community

Tokyo issues same-sex ‘partnership certificates’ amid cheers from LGBTQ community

“Forcing surgery that damages genitals against one’s will is a significant violation of human rights and [such a requirement] has been reviewed internationally,” said Yuko Higashi, professor at the Osaka Metropolitan University specialising in sexology.

“The Supreme Court said that the clause effectively requiring surgery to remove reproductive capacity for a person to change gender is unconstitutional, but it should have also said the clause mandating that the genitals closely match that of the gender the individual seeks is unconstitutional,” Higashi said.

Miura, one of the three justices who said the resemblance requirement clause violates the constitution, noted in his opinion that even without the clause, bath operators could still decide what policy to take, adding that there is little need to impose restrictions in law on people seeking to change gender.

Justice Koichi Kusano stated in his opinion that the clause likely existed so that people would not feel embarrassed or uncomfortable at the sight of genitalia of the opposite sex in places such as public baths.

But a “serene society” has only been realised at the expense of constant oppression of the liberties of people with gender dysphoria, Kusano said.