Lia Thomas' attempt to challenge World Aquatics' policy for transgender athletes has been dismissed. Thomas, a transgender woman, argued the ruling was discriminatory and took legal action against it earlier this year, but the Court of Arbitration for Sport ruled this week she is not entitled to challenge the rules.

Thomas has not registered to compete in any World Aquatics events and is no longer a member of US Swimming, according to the ruling obtained by CBS News. Thomas, the court said, is "not sufficiently affected by the rules" and therefore cannot challenge them. 

The Court of Arbitration for Sport, or CAS, says transgender women can compete in World Aquatic events under two conditions: they did not experience male puberty or their male puberty was suppressed before age 12, and their testosterone levels are consistently below 2.5nmol/L.

USA Swimming's policy states transgender women must have less than 5 nmol/L of testosterone consistently for 36 months before they can compete at elite levels. But the policy also states that to compete in international events, a transgender woman must meet World Aquatics criteria.

In 2022, World Aquatics voted to prevent trans women who have gone through any male puberty from competing in elite events, according to BBC News.

When Thomas filed her challenge to the ruling earlier this year, the court said she "accepts that fair competition is a legitimate sporting objective and that some regulation of transgender women in swimming is appropriate." But she argued that the provisions she was challenging were invalid and unlawful as they discriminate against her.

CBS News has reached out to World Aquatics, CAS and a attorney for Thomas and is awaiting response.

Thomas was a star on the University of Pennsylvania swim team, earning the best 200-meter freestyle time in the 2022 NCAA season and finishing nearly 40 seconds ahead of her closest competitor in one race. 

Thomas previously swam on the men's team and followed NCAA and Ivy League rules when she began transitioning in 2019. Thomas said during a podcast interview that her coach, Mike Schnur, and team were "unbelievably supportive since the beginning." Both the university and the Ivy League also released statements supporting Thomas.

But her competing on the women's team was also met with criticism. While a group of her teammates penned a letter of support, 16 U Penn athletes wrote an anonymous letter to the NCAA saying she should not be allowed to swim on the women's team.

The issue sparked debate among other athletes and non-athletes. Eighteen-time tennis Grand Slam winner Martina Navratilova wrote on social media that it's "not fair for women to race against transgender Lia Thomas." 

Olympic gold medalist Caitlyn Jenner, who came out as a trans woman in 2015, said "we need to protect women's sports," when talking about Thomas. 

Schuyler Bailar, who became first trans athlete to compete on a NCAA Division 1 men's team when he swam for Harvard, has supported Thomas, whom he once competed against. He said while she receives backlash, many of the messages Thomas receives are positive and sympathetic. 

"The story is that trans women are going to destroy women's sports, and that's also just false," Bailar said. "People want to police the women's category. People care a lot about what they think constitutes womanhood, and a lot of people want to police exactly what womanhood looks like, and end up policing trans women as a result."

Caitlin O'Kane

Caitlin O'Kane is a New York City journalist who works on the CBS News social media team as a senior manager of content and production. She writes about a variety of topics and produces "The Uplift," CBS News' streaming show that focuses on good news.