The organization behind international swimming, FINA, announced a ban on trans women athletes from competing in women's events if they did not transition by 12.
FINA's policy starts Monday, according to a copy of the new regulation.
Members at the body's congress in Budapest voted with a little over 70 percent supporting the new policy after a presentation from medical and legal experts and two athletes, Cate Campbell and Summer Sanders, who FINA said supported the regulation.
The three groups had been collaborating to create the policy after the International Olympic Committee set out recommendations examining the "advantages" of trans athletes, according to the FINA. The IOC had discouraged the "reliance on testosterone" levels.
"They're not saying everyone should transition by age 11, that's ridiculous. You can't transition by that age in most countries and hopefully you wouldn't be encouraged to. Basically, what they're saying is that it is not feasible for people who have transitioned to compete without having an advantage," James Pearce, a spokesperson for FINA president Husain Al-Musallam, told the Associated Press.
Pearce noted that there are no trans women who compete at the top in international swimming.
The swimming body's new policy also included a possible "open competition" category. It said a working group would be put together to determine how best to set the category up.
"No one quite knows how this is going to work. And we need to include a lot of different people, including transgender athletes, to work out how it would work," Pearce said. "So there are no details of how that would work. The open category is something that will start being discussed tomorrow."
In a statement, the Human Rights Campaign condemned the new policy. It stated that demanding trans athletes to transition by age of 12 is "an unrealistic and effectively impossible requirement especially as some states, including Alabama and Arkansas, are attempting to ban transgender youth from accessing the very same age-appropriate, medically necessary gender-affirming care that would allow them to comply with this policy."
"This sudden and discriminatory decision is a blatant attack on transgender athletes who have worked to comply with longstanding policies that have allowed them to participate for years without issue," said Joni Madison, HRC's interim president. "This policy is an example of swimming organizations caving to the avalanche of ill-informed, prejudiced attacks targeted at one particular transgender swimmer. We urge the FINA to rethink its policy and ensure inclusion for all athletes -- including transgender women -- and allow them to participate in sports free from discrimination, abuse, and harassment."
FINA's policy will change the sports career of Lia Thomas, the first out trans woman to win a NCAA Division I women's swimming championship. She's told several outlets that she'd like to continue swimming after college and even make try for the Olympics.