Switzerland's top court said Monday it had temporarily suspended IAAF rules that oblige athletes including double Olympic champion Caster Semenya to lower her testosterone levels in order to compete in certain events.
Swiss Federal Tribunal spokesman Peter Josi told AFP that the court had issued a "super-provisional order," barring the application of the rules introduced by the International Association of Athletics Federations until a further hearing can take place.
The IAAF measures were previously approved by the Lausanne-based Court of Arbitration for Sport (CAS).
Judges at the sports court agreed that the rules were "discriminatory" but found, in a split decision, that they were "necessary" to ensure fairness in women's athletics.
Semenya, the South African who won the women's 800 metres at the 2012 and 2016 Olympics, last week announced plans to appeal to Switzerland's highest court.
"I am thankful to the Swiss judges for this decision," Semenya said in a statement issued by her legal team.
"I hope that following my appeal I will once again be able to run free," she added.
The new IAAF rules require women with higher than normal male hormone levels to artificially lower the amount of testosterone in their bodies if they are to compete in races over distances of 400m to the mile.
The reprieve granted by the court in Bern also applies to the two women who finished behind her in the 800m at the 2016 Rio Olympics, Burundi's Francine Niyonsaba and Margaret Wambui of Kenya.
"It is fantastic news," Semenya lawyer Gregg Nott told the South African 702 radio station.
"She can run the races that she was told that she cannot run," he added, citing the 400m and 800m.
The IAAF said in a statement it had "received no information from the Swiss Federal Court so we can not comment at this stage."
The Swiss ruling is designed to have a short shelf-life.
The IAAF and Semenya's camp must now make further submissions to the court, which will decide on whether to order a longer suspension of the measures.
The court is due in the coming weeks to issue another decision on whether to extend the suspension.
Swiss justice moves slowly, meaning a final ruling on the admissibility of the IAAF measures could take years.
"This is an important case that will have fundamental implications for the human rights of female athletes," Semenya's Swiss lawyer, Dorothee Schramm, said in the statement.