Swimming's world governing body, Fina, has dropped its investigation into the results of an Ian Thorpe drugs test because of a lack of evidence.
Thorpe denied ever taking performance-enhancing drugs
Thorpe, who won five Olympic gold medals, showed abnormal levels of testosterone and leutenising hormone in a drugs test last year.
He strenuously denied any wrongdoing, and submitted a strong defence to Fina.
"There's not sufficient evidence to take further action," a Fina executive director told the Australian newspaper.
Fina had been looking at taking the case to the Court of Arbitration for Sport, but has now abandoned the idea.
"The case is now closed and there is no question of it being opened again," a Fina spokesman told BBC Sport.
The 25-year-old had already been cleared by the Australia Anti-doping Authority (ASADA) in August, with medical experts deciding that the substances had occurred naturally.
Both testosterone and leutenising hormone are on the banned list but are naturally produced by the body.
Thorpe, Australia's most successful Olympian of all time, retired from the sport last year, citing injury and fatigue.