LaShawn Merrit, the 2008 Olympic 400m Champion,  was suspended from all completion for 18 months in 2010 after being found guilty of taking a 'prohibited substance'.

Under International Olympic Committee (IOC) Rule 45 introduced to the Olympic Charter in 2008, any athlete found guilty of a doping offence is  automatically banned from participating in the following Olympics if the ban exceeds 6 months.

Merritt's doping ban ends in July 2011 but under current  IOC rules he would still be ineligible for the London Olympic games in July 2012.

The arguments

Merritt is seeking to challenge this rule. Opponents of the rule contend that it is too severe as it effectively extends the ban of the convicted athlete even further than the original sanction imposed.  Furthermore they argue that it amounts to a double hit for the same offence and that it is contrary to 'natural justice'.

American Swimmer Jessica Hardy who missed the 2008 Olympics due to a doping violation has already been cleared to compete in London 2012. However her case has been distinguished from others as the IOC notified her that she was not subject to their rule as it had come into effect at the same time as her positive test. Incidentally, Hardy is represented by Howard Jacobs who is the same lawyer representing Merritt.

A previous decision by CAS in 2008 ruled that he European Athletic Association had illegally  imposed an additional sanction by banning suspended athletes from its next European Championship.

The IOC meanwhile counter that the further prohibition on participation in the next Olympics is not a double sanction but an eligibility issue rule.

When it will be heard

The IOC and US Olympic Committee agreed to send this matter to CAS on 28 April 2011. Both parties want an early ruling in order to avoid legal issues before the London Olympics.

Implications for Sport

The 2008 CAS decision would suggest that Merritt may be successful in his appeal  but it remains to be seen what the outcome will be.

If CAS rule against the IOC, then convicted drug cheats will be free to compete in the Olympics once their ban has ended.

The British Olympic Association has previously imposed a lifetime Olympic ban for any athlete with a failed drug test and this policy would surely have to change if CAS ruled against the IOC.

High profile athletes like Dwain Chambers, David Millar and Tim Don have all fallen foul of this rule in the past but now such athletes would be allowed compete in the Olympics if the IOC rule is overturned.