The I.A.A.F. had argued that athletes classified with “differences of sexual development,” also known as intersex athletes — particularly women who possess testes and natural testosterone levels in the male range — gain an unfair advantage in women’s events ranging from 400 meters to one mile because they have additional muscle mass, strength and oxygen-carrying capacity.

But the sports court expressed some “serious concerns” on Wednesday about the fairness and practical application of testosterone limits. These concerns include the potential inability of athletes to remain within permitted limits even with hormonal treatment and the “practical impossibility” of compliance some athletes may face because of the treatment’s side effects.

The court also expressed concern about a lack of concrete evidence that athletes with differences of sexual development gain a significant advantage at longer race distances — 1,500 meters and the mile. The panel asked that the I.A.A.F. consider deferring application of its testosterone rule beyond 800 meters “until more evidence is available.”

Semenya, 28, issued a statement through her lawyers, saying: “I know that the I.A.A.F.’s regulations have always targeted me specifically. For a decade the I.A.A.F. has tried to slow me down, but this has actually made me stronger. The decision of the C.A.S. will not hold me back. I will once again rise above and continue to inspire young women and athletes in South Africa and around the world.”

[Read more about Semenya’s early life, and what she means to South Africa.]

Her lawyers said they might appeal Wednesday’s decision, arguing that “her unique genetic gift should be celebrated, not regulated.” Semenya can appeal to the Swiss Supreme Court on narrow grounds.

The I.A.A.F. accepts athletes with differences of sexual development as legally female. For competitive purposes, though, it effectively considers them biologically male. The I.A.A.F. has said this is necessary to provide a level playing field in races that can be won by a hundredth of a second. To do nothing, it has said, risks “losing the next generation of female athletes.”