Former world record holder and Olympic gold medallist Roland Schoeman has been given a one-year ban after testing positive for a prohibited substance.
The 39-year-old South African won 4x100m relay gold at Athens 2004.
He tested positive in May last year for GW501516, classed as a hormone and metabolic modulator.
The ban is backdated and ends on 17 May, meaning he would be eligible for the Tokyo Olympic swimming event starting on 25 July.
Schoeman, who represented South Africa in four successive Games from 2000-12 but failed to qualify for the 2016 Rio Olympics, is also a triple world champion and has held world records in butterfly and freestyle.
The World Anti-Doping Agency alerted athletes in 2013 that GW501516 failed medical trials and was a toxic threat to health if used as a performance enhancer.