According to IOC regulations athletes are not allowed to participate in any marketing campaigns other than those endorsed by the IOC between 18th July and 15th August. The two images were leaked on 13th August just days before the restrictions were meant to be lifted.
Louis Vuitton and Phelps' management have adamantly denied that the images were officially released and that they were in fact stolen and leaked via Twitter without their knowledge. (Both parties would surely have to say this to cover their backs, no?)
Phelps doesn't look so golden now... but he does look pretty tasty if I say so myself!