The latest transgender-rights battle is taking place in a courtroom at Edinburgh, as Scotland seeks to become the first part of the United Kingdom to break away from Westminster’s law and make it far easier for people to change their gender without a medical diagnosis of “gender dysphoria.” 

The Scottish and the United Kingdom governments are facing each other in a three-day hearing that started on Tuesday after the U.K. blocked Scotland’s Gender Recognition Reform bill, which was approved in the Scottish parliament in December. The bill removes obstacles for people wanting to legally change their gender. Westminster argues it will reduce protection for single-sex spaces and have “ramifications” for U.K.-wide equality law. 

Currently, people in the United Kingdom can legally change gender if they are older than 18 and have been living as their identified gender for two years or more. They must also apply to a gender recognition panel — mostly composed of legal and medical professionals — and present a medical diagnosis of gender dysphoria. 

Scotland’s new legislation would remove the requirement of a gender dysphoria diagnosis and extend the application process to 16- and 17-year-olds. The bill also says they must have lived under their preferred gender for only three months — six months for those under 18 — to apply for a gender recognition certificate.  

Since the 2004 Gender Recognition Act has been in place in the U.K., only 4,910 transgender people have received a certificate, according to the government’s equalities office. The tentative estimate of transgender people in the United Kingdom is 200,000 to 500,000. 

The bill was approved in Scotland’s Holyrood parliament in December, six years after it was first introduced by Prime Minister Sturgeon. Despite internal conflict in the governing party —  a minister, Ash Regan, quit his position to protest against it — the bill received approval from the Scottish Greens, the Labour Party, and the Scottish Liberal Democrats. 

Eleven European countries have passed similar legislation, including Spain, Finland, and Belgium. The German government approved last month a proposal to eliminate the requirement for two psychological assessments for people to be allowed to change gender.

Following the December vote in Scotland’s parliament, the members of Holyrood worked for two days to make more than 150 amendments to the bill to address concerns over the impact on the U.K.’s equality law and abusive men taking advantage of the system. Yet, it still received backlash, particularly from Scottish Conservatives.

“In the rush to make the process a little easier for trans people, the government is making it easier for criminal men to attack women,” a member of Scottish Conservatives, Rachel Hamilton, said. Critics say the bill would by make it easier for male criminals to enter women-only spaces such as bathrooms, locker rooms, and prisons.

Indeed, since the bill was approved, high-profile cases have emphasized the concerns over women’s security and access to female-only places under the new system. In January, a transgender woman who raped two women before transitioning, Isla Bryson, was initially detained in an all-female prison. The move triggered concerns among politicians, campaigners, and the United Nations special rapporteur.

In January, the Scottish secretary, Alister Jack, made an unprecedented use of the Section 35 of the 1998 Scotland Act, which allows the United Kingdom government to intervene in legislation that is believed to be incompatible with wider U.K. law. Government sources describe this tool as “the nuclear option,” according to Politico. 

In a 13-page document, Mr. Jack says the bill will create two parallels “and very different regimes” to issue a Gender Recognition Certificate in the U.K. It also says it could increase the potential “for fraudulent applications to be successful,” jeopardizing the safety of women and girls. 

Before resigning as prime minister in February, Ms. Sturgeon said she would challenge the order presented by Mr. Jack. Her successor, Prime Minister Yousaf, has been following her steps.

During the three days of proceedings, the Scottish government will present evidence to the judge, Shona Haldan, on why it believes the U.K. government shouldn’t have intervened. On the other hand, Westminster must prove the bill will affect the country’s wider law.

Once the judge announces her decision — which could take some weeks after the proceedings — the losing side can appeal to the U.K.’s supreme court.