American swimmer Lia Thomas has had a legal case against governing body World Aquatics dismissed by the Court of Arbitration for Sport.

World Aquatics (WA) voted in 2022 to stop transgender women from competing in women’s elite races if they have gone through any part of the process of male puberty.

Thomas, 25, who became the first transgender athlete to win the highest US national college title in March 2022, was attempting to overturn that ban at the Court of Arbitration for Sport (Cas), arguing the rules were discriminatory.

Cas first had to determine whether Thomas was eligible to challenge the rules.

In a 24-page verdict, Cas said 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, “let alone compete in a WA competition”, and therefore was “not sufficiently affected” by the rules to be able to challenge them.

WA praised the ruling and said it is 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,” a statement said.

“Our policies and practices are continuously evaluated to ensure they align with these core values, which led to the introduction of our open category.

“We remain committed to working collaboratively with all stakeholders to uphold the principles of inclusivity in aquatic sports and remain confident that our gender inclusion policy represents a fair approach.”