World Athletics will not allow transgender women who transitioned post-puberty to compete in female sports, organization President Sebastian Coe announced Thursday. Coe said it was “vital that we protected the female category.” However, Coe acknowledged the ban is preemptive as there currently aren’t transgender athletes in international competitions. The rule will go into place March 31, replacing the organization’s earlier precedent that transgender athletes can compete so long as they have sufficiently suppressed testosterone levels. Coe said the organization, which represents international cross country and track and field competition, said it is open to challenges but will “vigorously defend” its position.