Aleksey Troshkin won the event, held on 2 October, for the third consecutive year finishing in a time of two hours 18 minutes and 28 seconds.
However, his name is on an International Association of Athletics Federations list of athletes banned from international competition – which includes the Jersey Marathon.
The race is now under investigation by the IAAF.
The IAAF banned all Russian athletes from competing outside their home country following allegations of state-sponsored doping. There is no suggestion that Mr Troshkin has taken performance-enhancing drugs.
A £2,500 first prize was awarded to the Russian following his victory in the Jersey event.
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