Professional sports leagues, mindful of how they are seen, have every right and obligation to take care with their image. It is buying his behavior, the public image he portrays. Legislating appearance in sports is nothing new. Some coaches insist players wear suits on road trips. Others decry facial hair.
Athletes enjoy considerable personal time and the freedoms only exorbitant wealth can bring.
Nobody can insist an athlete be a positive role model if the role doesn't interest him. Allen Iverson is free to dress as he wishes on his own time. Not a pimp in a Dr. Dre video.