The case involves Russian long jumper Darya Klishina and the International Association of Athletics Federations (IAAF) concerning her eligibility to compete in international competitions, including the 2016 Rio Olympics. The dispute stemmed from systemic doping allegations in Russian athletics, leading to the suspension of the Russian Athletics Federation (RusAF) by the IAAF in November 2015. Under IAAF Rule 22.1A, athletes from suspended federations could seek exceptional eligibility if they proved they were outside Russia for a significant period and subjected to compliant drug testing. Klishina applied and was initially granted eligibility on July 9, 2016, by the IAAF Doping Review Board (DRB). However, following the release of the McLaren Report on July 16, 2016, which detailed state-sponsored doping in Russia, the DRB reconsidered its decision. The report included evidence suggesting Klishina’s samples had been tampered with, including a 2014 sample with a high T/E ratio and samples showing signs of cap removal and mixed urine. Based on this new evidence, the DRB revoked her eligibility on August 10, 2016. Klishina challenged this decision before the Court of Arbitration for Sport (CAS) ad hoc Division, arguing the revocation was unjust. The CAS panel examined whether the DRB had the right to revisit its decision based on new evidence and upheld the DRB’s authority under Swiss law and IAAF rules, emphasizing that new facts justified the revocation. The panel concluded that the DRB’s decision was valid, as the new evidence undermined the basis for Klishina’s initial eligibility. However, the panel later found that the new evidence did not negate Klishina’s compliance with the eligibility criteria, as the Rule focused on whether she was subject to compliant testing outside Russia, not on her involvement in the Russian system. The panel reinstated Klishina’s eligibility, allowing her to compete in the 2016 Olympics. The case highlights the legal principles surrounding the reconsideration of decisions based on emerging evidence and the strict enforcement of anti-doping regulations in international sports, while also underscoring the distinction between eligibility rules and doping allegations. The final decision affirmed Klishina’s right to compete, emphasizing the lack of evidence linking her to doping violations.