“Although athletics events are divided into discrete male and female categories, sex in humans is not simply binary,” the court added. “As it was put during the hearing: ‘Nature is not neat.’ There is no single determinant of sex.”

It continued: “Nevertheless, since there are separate categories of male and female competition, it is necessary for the I.A.A.F. to formulate a basis for the division of athletes into male and female categories for the benefit of the broad class of female athletes. The basis chosen should be necessary, reasonable and proportionate to the legitimate objective being pursued.”

Chand, an 18-and-under national champion in the 100 meters and an Olympic hopeful, was found to have hyperandrogenism and barred from competing against women in 2014 because her natural levels of testosterone exceeded guidelines for female athletes. Now, Chand and other women who may have similar conditions can participate in international competition, perhaps including next year’s Summer Olympics in Rio de Janeiro.

“What I had to face last year was not fair,” Chand said Monday in a statement released by Davies Ward Phillips & Vineberg L.L.P., a Toronto law firm that represented her. “I have a right to run and compete. But that right was taken away from me. I was humiliated for something that I can’t be blamed for. I am glad that no other female athlete will have to face what I have faced, thanks to this verdict.”

The panel was ruling specifically on track and field’s regulation, but the Court of Arbitration for Sport’s wide jurisdiction means its decision is likely to serve as a precedent for other sports around the world.

It was just the latest high-profile case to confront the intensely disputed boundaries of fairness in track and field in recent years. The South African sprinter Oscar Pistorius, for example, eventually won the right to compete at the 2012 Summer Olympics in London using prosthetics. In a case more clearly linked to that of Chand, the South African runner Caster Semenya in 2009 was barred from competition and reinstated nearly a year later after a series of sex tests and much publicity.