It was a landmark decision handed down by the highest court in international sports. Now, Caster Semenya, 28, a female South African Olympic gold-medalist in the 800 meter, will not be able to compete unless she takes hormone therapy. The questions over her sex started in 2009 when at 18 years-old she won gold in the 800 meter at the World Track and Field Championships.
In 2012, she won silver in the Olympics, but because the Russian woman who won gold was doping, Semenya moved up to gold.
In 2016, at the Olympics in Rio, she won gold again in the 800 m.
Since then, she has been fighting the highest governing body in sport, the International Association of Athletics Federations.
It's been reported that Semenya has abnormally high naturally occurring testosterone for a woman, known as hyperandroginism.
The IAAF sees this as a fairness problem. So last year it added new rules that women with "differences of sex development," also known as "46, XY DSD athletes," need to take drugs to lower their testosterone to compete in the 400m, 800m, 1500m or mile.
Semenya appealed the rule, and Wednesday, the highest court in sport dismissed the appeal saying ""such discrimination is necessary, reasonable and proportionate means of achieving" integrity of female athletics.
The IAAF said it was "grateful" for the ruling.
We connected with Virginia Jackson, a sports historian and lecturer at Arizona State University and a former pro track athlete.
"The Olympics and these international competitions are a celebration of the exceptional, but when the exceptional relates to gender they are like 'no, this is an unfair competitive advantage."
She brings up the example of Eero Mantyranta, a four-time Olympian in cross country skiing who was suspected of doping but was proven to have a genetic mutation that allowed his bone marrow to process 50-percent more red blood cells than normal. It's a trait passed down to relatives who also dominated in skiing.
There was no rule for him.
The problem, seen by Jackson and others, is about splitting sports into male and female when nature and genetics are more complicated than that.
"Women have had to prove they are women to compete in the women's categories since the 1940s. It's been virtually impossible to identify one determining factor in order to clear women for competition in the women's category. Men don't have to prove they are men. Women have to prove they are women," said Jackson.