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 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 US swimming.

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