Breaking News:NCAA Lia Thomas has lost all her medals, Riley Gaines will get them all thanks to outside forces…See More

The US swimmer Lia Thomas, who rose to global prominence after becoming the first transgender athlete to win a NCAA college title in March 2022, has lost a legal case against World Aquatics at the court of arbitration for sport – and with it any hopes of making next month’s Paris Olympics.

The 25-year-old also remains barred from swimming in the female category after failing to overturn rules introduced by swimming’s governing body in the summer of me 2022, which prohibit anyone who has undergone “any part of male puberty” from the female category.

Thomas had argued that those rules should be declared “invalid and unlawful” as they were contrary to the Olympic charter and the World Aquatics constitution.

However, in a 24-page decision, the court concluded that Thomas was “simply not entitled to engage with eligibility to compete in WA competitions” as someone who was no longer a member of USA swimming.

The news was welcomed by World Aquatics, who hailed it as “a major step forward in our efforts to protect women’s sport”.

“World Aquatics is dedicated to fostering an environment that promotes fairness, respect, and equal opportunities for athletes of all genders and we reaffirm this pledge,” it added.

World Aquatics introduced its new rules after Thomas beat Olympic silver medalist Emma Weyant by 1.75sec to win NCAA gold in the women’s 500-yard freestyle in 2022.

In a scientific document that informed its decision, it said swimmers such as Thomas retained significant physical advantages – in endurance, power, speed, strength and lung size – from undergoing male puberty, even after reducing their testosterone levels through medication.

While it is understood that World Aquatics was prepared to argue the merits of the scientific evidence at Cas, the hearing solely focused on whether Thomas, who is no longer a member of USA swimming, was allowed to challenge its rules.

On Wednesday it ruled that Thomas had no standing to sue World Aquatics’ transgender policy, with a key paragraph stating: “The panel concludes that since the Athlete is not entitled to participate in ‘Elite Event’ within the meaning of USA Swimming Policy, let alone to compete in a WA competition, which occurs upon registration with WA prior to a competition or upon setting a performance which leads to a request for registration as WA world record, she is simply not entitled to engage with eligibility to compete in WA competitions.

The policy and the operational requirements are simply not triggered by her current status.”

World Aquatics insists it is doing all it can be inclusive and has introduced an “open” category for transgender swimmers. However, plans to debut it at the Berlin World Cup last October were cancelled after no entries were received for any of the 50m and 100m races across all strokes, which were due to take place alongside male and female races.