In one leap, Denmark has changed its law on trans rights, taking it from a country where transgender people were forced to undergo sterilisation in order to be legally recognised as a different gender, to one of the most progressive countries on the issue in the world.

Unlike in most of the countries that allow new gender recognition, trans people in Denmark now do not even need a medical expert statement, but can simply self-determine. There are still restrictions – the minimum age is 18, and there is a six-month waiting period before the person has to reconfirm their wish to have their gender legally changed – but the law seems to be moving in the right direction.

But Denmark's new law – which came into force on Monday – raises questions for the other European countries where forced sterilisation – either as a result of hormone treatment or surgery – is still the only route for someone transitioning to gain legal status. This requirement ignores the fact that many trans people don't want to undergo a major operation, or to irretrievably lose their fertility as a result of it, as part of their transition.

Why is sterilisation still insisted on? "There is still a strong belief in gender segregation, so people think it should be made as difficult as possible for trans people to change documents," says Richard Köhler, senior policy officer of Transgender Europe, a human rights NGO. There is also a fear in some countries that married people who seek gender recognition will result in same-sex marriages (forced divorce is also often insisted upon, or in countries where it is possible, forced conversion to a civil partnership).

"Historically, the first law in western Europe that introduced gender recognition was in Sweden and they included forced sterilisation, coming clearly from a time where sterilisation of other groups in Sweden was in full swing, and this became the blueprint for other laws in western Europe." While there probably are minority groups who believe in sterilisation, Köhler believes the bigger issue is "really related to ignorance and how little fact-based debate there is about trans issues."

In May, an inter-agency report by the World Health Organisation and the UN among others described forced sterilisation as a violation of human rights, running "counter to respect for bodily integrity, self-determination and human dignity."

Change is happening, although slowly. Sweden dropped its sterilisation requirement last year, and this year the Netherlands changed the law to allow people to change their gender on official identity papers without the need for hormone therapy or surgery (though they still need to obtain a medical statement).

But there are still 20 European countries where sterilisation is a requirement, including much of eastern Europe (and some, including Ireland, don't even have legal recognition for transgender people). Here are just a few:

France

Consistency is a problem in France, with some courts requiring people to have had gender confirmation surgery (which results in sterilisation) before they get legal gender recognition. Even without surgery, psychiatric diagnosis and some form of irreversible treatment (such as hormone treatment, which could amount to "chemical castration") is needed by courts.

One transgender man told Amnesty International, for its report The State Decides Who I Am, which was published this year, that getting a diagnosis of "transsexualism" – which is needed before a person can access treatments, and therefore legal recognition – was "basically a process aimed at getting a paper certifying that you are insane".

Finland

In order to legally change gender, transgender people in Finland must obtain a psychiatric diagnosis of "transsexualism". This allows them to access hormone treatment – again, compulsory if they wish to change their legal gender.

Norway

The Oslo University Hospital is where transgender Norwegians seeking a legal change of gender will find themselves. It is the only place in the country where people can get a psychiatric diagnosis and gender confirmation surgery (ie sterilisation) which are mandatory legal requirements. Failing to get a diagnosis (and being the only place in the country, there are no second opinions) means a person cannot access trans-related healthcare – if they wanted gender reassignment surgery, they would have to seek it abroad.

Belgium

Similarly, transgender people in Belgium must get a psychiatric diagnosis, followed by hormone treatment, surgery (resulting in sterilisation) and pass a "real life" experience test (living in the self-determined gender for a period of time).

Czech Republic

"The Czech Republic unfortunately increased the barriers and made it much more difficult for legal gender recognition," says Köhler.

The new Czech Civil Code, which came into force in January this year, codified the practices that lead to legal gender recognition, which includes mandatory surgery. This is perhaps surprising; the Czech Republic is known for being fairly liberal with regard to LGBT issues. "Absolutely. This is what I'm talking about – the ignorance," says Köhler. "There are a lot of people who would, if they knew about it, be up in arms against forced sterilisation."