The national governing body for competitive swimming in the US has updated its policy for transgender female athletes.
USA Swimming - who sets rules and guidelines for athletes all the way up to Olympic level - released the Athlete Inclusion, Competitive Equity, and Eligibility Policy on Tuesday, which takes effect immediately.
The new policy has already been criticized by transgender advocates because it means that Lia Thomas - a trans swimmer at the University of Pennsylvania who was on track to win big at the NCAA championships - will likely be disqualified.
According to the new policy, there are two requirements that trans women must meet in order to compete as members of USA Swimming.
The first is that the concentration of testosterone in their blood is consistently below 5 nanomoles per liter for 36 months before competing.
They must also provide evidence that going through puberty has not given them "a competitive advantage over [their] cisgender female competitors."
All applicants are subject to a reviewing panel of three independent medical experts who will decide whether or not they are eligible to compete.
Thomas - who this season swam the fastest time in the U.S. in both 200-yeard and 500-yeard freestyle - will only have completed 34 months of hormone therapy by the time of the NCAA Championships in March 2022, making the chances of her being allowed to compete low.
Trans runner Joanna Harper hit out at USA Swimming's policy, saying: "I doubt that it is a coincidence that Lia will have had 34 months of hormone therapy by March 2022," in an email, per CNN.
Harper - who is also a visiting fellow for transgender athletic performance at England's Loughborough University - further criticized the 36-month requirement, saying there is no proof to suggest it "will be any more effective in mitigating advantages than 24 months would be."
Many on Twitter agreed that USA Swimming was targeting Thomas and caving to her critics.
"This was a decision SOLELY to eliminate Lia Thomas from the team," one person wrote.
"It's hard not to see how this policy wasn't directly targeted at Lia Thomas," tweeted another.
"Not to mention, any trans female athlete transitioning in college will essentially forfeit all sports competition due to a 3 year bar which would basically be all of college," they added.
However, others have praised the policy change. Olympic swimming champion Nancy Hogshead-Makar - who founded legal advocacy group Champion Women - tweeted that USA swimming "deserves our appreciation for prioritizing biological women in new eligibility guidelines."
Meanwhile, reports suggest it is uncertain exactly how the new policy will apply to Thomas given that she has followed all previously established rules in the run-up to the NCAA Championships.