Riders who were assigned male at birth will be prevented from racing in British Cycling's elite female events under a new transgender and nonbinary participation policy published by the governing body Friday.
New rules for competitive events, due to be implemented this year, will see racing split into "open" and "female" categories, with transgender women, transgender men, nonbinary individuals and those whose sex was assigned male at birth eligible to compete in the open category.
The female category will remain for those whose sex was assigned female at birth and for transgender men who have not begun hormone therapy.
The current men's category will be consolidated into the open category, in which those whose sex was assigned as female at birth can also compete if they so wish.
British Cycling suspended its previous policy last April after transgender woman Emily Bridges sought to race at the national omnium championships as a female rider. British Cycling CEO Jon Dutton apologized for the anxiety and upset caused during the 13 months since.
The policy is the result of a nine-month review that included a consultation process with cyclists and stakeholders, including members of Britain's team, as well as a study of available medical research led by British Cycling's chief medical officer, Dr. Nigel Jones. That research was said to show a clear performance advantage for individuals who go through puberty as a male, one that cannot be fully mitigated by testosterone suppression.
British Cycling's previous transgender policy allowed riders to compete in the female category if they had testosterone levels below five nanomoles per liter for a 12-month period prior to competition.
The governing body will continue to study new research as it becomes available with the policy being regularly reviewed.
"It's an incredibly emotive and at times divisive subject area," said Dutton, who has been in his post for one month. "We have taken many months to look at three areas: firstly a consultation with the athletes affected and the wider cycling community; secondly looking at the medical research available at this point in time; and thirdly from the legal viewpoint in terms of the association with the Equalities Act.
"We've made a decision on the balance of all three to give clarity, to give direction and that clear way forward for any athletes affected."
Bridges condemned the rule changes in a scathing Instagram post Friday, calling British Cycling a "failed organisation."
"British Cycling has just banned us from racing," she wrote. "... They have no authority to control this conversation anymore."
There is no set date for the new regulations to be implemented, with the governing body saying only that it will be before the end of the year, allowing time for changes to technical regulations and discussions with the UCI, cycling's world governing body, regarding implementation.
The new policy diverges from that of the UCI, which promised to look again at its own regulations after American transgender woman Austin Killips won the Tour of the Gila in New Mexico this month.
The UCI allows transgender women who have gone through male puberty to compete in elite women's events if they have had reduced testosterone levels of 2.5 nanomoles per liter for the previous two years.
The Associated Press and Reuters contributed to this report.