Tour de France director Christian Prudhomme made the decision to ban Boonen from this years race after discussing the situation with the rider and his team.
This revelation means now two of the jersey winners from last year's Tour de France will not be allowed to defend their titles. The first rider to earn this distinction was Spaniard Alberto Contador, who rides from the controversial Astana team. The second being Boonen, Green Jersey winner from last years competition.
While Boonen is not being accused of cheating since the test was out of competition, and the recreational drug isn't on the banned list, he will still have to answer to the Belgian authorities on the matter.
The rider was given the support of his Quick Step team as well as the top brass of the Quick Step company.