Athletics' world governing body has submitted a request to overturn an order allowing Caster Semenya to temporarily compete without taking testosterone-reducing medication.
Switzerland's federal supreme court had suspended an IAAF ruling restricting testosterone levels in female runners.
It meant South Africa's double 800m Olympic champion Semenya could continue to compete pending a final judgement.
The IAAF said it had submitted its response to the Swiss Federal Tribunal.
South African Semenya had filed an appeal to the Swiss court last month after her attempt to have new IAAF rules restricting testosterone levels in female runners overturned by the Court of Arbitration for Sport (Cas) was unsuccessful.
Semenya said afterwards: "I hope following my appeal I will once again be able to run free.
"I am thankful to the Swiss judges for this decision."