Lia Thomas, a transgender-identifying swimmer, cannot compete in high-ranking women’s races.

Thomas previously challenged World Aquatics’ ban on transgender swimmers who have been through puberty. The biological male alleged that the policy was discriminatory.

The Court of Arbitration for Sport ruled that Thomas “lacks standing to challenge the policy and the operational requirements in the framework of the present proceeding,” adding that USA Swimming could not “modify such scope of application” to its rules, according to Associated Press.

World Aquatics said the ruling is a “major step forward in our efforts to protect women’s sport.”

Thomas said the decision was “deeply disappointing,” noting that the bans against transgender individuals are “discriminatory and deprive us of valuable athletic opportunities that are central to our identities.”

Former collegiate swimmer and women’s sports advocate Riley Gaines declared the ruling was a “victory for women and girls everywhere.”

“Great news! Lia Thomas won’t be able to compete in women’s category at the Olympics or any other elite competition,” she wrote on X. “He has just lost his legal battle in Court of Arbitration for Sport ruling.”

“This is a victory for women and girls everywhere.”

She added in a subsequent post that the NCAA “needs to strip him of every award, title, and record he stole from a deserving female athlete.”