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Swimmer Lia Thomas had her attempt to overturn a World Aquatics policy barring her from competing in women's races dismissed. Thomas, who is a transgender woman, argued the policy is discriminatory and wanted to take legal action against it earlier this year.

However, the Court of Arbitration for Sport ruled that Thomas isn't permitted to challenge the policy.

According to CBS News, Thomas hasn't registered to compete in any World Aquatics events and also is no longer a member of the US Swimming.

The CAS states transgender women can compete in World Aquatics events if they meet two guidelines. Those are that they didn't experience male puberty and their testosterone levels are below 2.5nmol/L.

US Swimming's policy states transgender women have to have less than 5 nmol/L of testosterone on a consistent basis over a 36-month period to compete at elite levels. However, the policy also makes it clear that to compete in international events, a transgender woman must meet the criteria set in place by World Aquatics.

According to a BBC News report, World Aquatics voted in 2022 to prevent transgender women from competing in elite events if they went through male puberty.

Thomas swam for the University of Pennsylvania swim team and was the first openly transgender athlete to win an NCAA Division I national championship. She won the women's 500-yard freestyle event in 2022.

Thomas previously swam on the Quakers men's team, but she followed NCAA and Ivy League rules when she began to transition in 2019.