Olympic Gold medallist Caster Semenya has lost an appeal against rules limiting levels of testosterone in female athletes.
In order to compete in competitions under the International Association of Athletics Federations (IAAF) Semenya will now need to take drugs to suppress levels of the hormone.
Julian Savulescu, a professor of practical ethics at the University of Oxford, believes the rules are unfair and lack justification.
Speaking to Belle Donati, before the Court of Arbitration in sport confirmed the news, he said measures should not be introduced that destroy the careers of athletes who have done nothing wrong.
"Many of the gold medallists throughout history will have had a condition like Semenya"
"I think it's one thing to change the rules prospectively but not to ruin the lives of athletes who are already in competition."
Using testosterone levels to decide who can compete in female sport raises fundamental questions about our attitude to gender, he added, asking:
"Are we going to disadvantage these people who we've judged to be women by stopping them competing in sport or are we going to change our definition of what is a man and what is a woman?"