The former sprint champion Michael Johnson says doping authorities should bring their rules into line with the International Olympic Committee to prevent convicted cheats competing at the Olympics.
The Court of Arbitration for Sport cleared the way in October for dozens of convicted dopers to compete at the Games when they rejected an IOC eligibility rule as invalid.
The rule, which was introduced in 2008, banned athletes from competing at the next Olympics if they had served a suspension for doping of six months or longer.
The court said the Olympic ban was not in line with the World Anti-Doping Agency's code.
Critics of the IOC eligibility rule said it acted as a double punishment, with athletes serving suspensions and then being forced to miss the Olympics.
But Johnson, a four-time Olympic gold medal winner, believes it is fair that athletes who have been caught cheating miss an Olympics and says CAS probably had its hands tied.
He says the IOC is going to have to go back and work with the doping agency to get that eligibility rule as part of its code.
He believes WADA and CAS both share the goal to deter people from using drugs but says there needs to be coordination between the organisations so that everyone is on the same page.