The case involves a professional tennis player who appealed a decision by the Association of Tennis Professionals (ATP) after testing positive for cocaine metabolites during a tournament in Chile in February 2004. The player claimed he had consumed coca tea and leaves to alleviate altitude sickness and was unaware they contained prohibited substances. The ATP's Anti-Doping Tribunal found him guilty under strict liability rules, disqualifying his results and imposing a two-year suspension. The player appealed to the Court of Arbitration for Sport (CAS), arguing no fault or negligence or, alternatively, no significant fault or negligence, seeking to overturn or reduce the penalty. The CAS upheld the ATP's decision, emphasizing that athletes are strictly liable for any prohibited substances in their bodies, regardless of intent or knowledge. The panel ruled that the player, as a professional athlete, had a duty to ensure no banned substances entered his system, even if consumed for medicinal purposes. The fact that the substance was natural (coca leaves) did not exempt him from responsibility, as the prohibited substances list does not need to specify every derivative. The CAS also rejected the argument that the ATP should have warned athletes about natural products, stating that education efforts do not relieve athletes of their individual responsibility. The CAS confirmed the two-year suspension and disqualification of results, noting the player's negligence was significant and did not meet the criteria for reduced sanctions. The decision reinforced the principle of strict liability in anti-doping regulations, underscoring that athletes must exercise extreme caution with any substance they ingest. The ruling serves as a reminder of the high standards expected of professional athletes in adhering to anti-doping policies. The panel also addressed the start date of the ineligibility period, ultimately adjusting it to begin from the date of sample collection (9 February 2004) rather than the decision date, acknowledging fairness concerns. The case highlights the tension between harmonized sanctions and individual justice within the anti-doping framework, emphasizing the importance of fairness when athletes do not intentionally seek an unfair advantage. The final ruling partially allowed the appeal, modifying the original decision to reflect the adjusted period of ineligibility and the forfeiture of results from the sample collection date onward. The decision underscores the strict liability principle and the limited exceptions available under the current anti-doping regulatory framework.