Back to the basics in GB?
Much more complicated than that.
The case - which focused on the proper interpretation of the 2010 Equality Act - began in 2018.
This was after Scottish Parliament passed a bill designed to ensure gender balance on public sector boards.
For Women Scotland then complained that ministers had included transgender people as part of the quotas in that law.
The campaign group argued this would have wider implications for the single-sex spaces and groups, such as hospital wards and prisons - where transgender women with a gender recognition certificate would be treated as biological women.
Transgender people, meanwhile, warned the case could erode the protections they have against discrimination in their reassigned gender.
The appeals
The issue was then contested several times in the Scottish courts - where the campaign group's arguments failed to change the law.
In the meantime, heated debate around the separate arguments on the subject arose, including an ongoing employment tribunal involving a female NHS Fife nurse who objected to a transgender doctor using a women's changing room.
The Supreme Court - today's verdict
On appeal, the case finally arrived at the Supreme Court in London, where the judges today ruled against the Scottish government and in favour of For Women Scotland.
As we've been reporting, the judgement unanimously ruled that a woman is defined by biological sex under equalities law.