How to report a cheater on WII
Report the problem to Nintendo. Although there isn't any official way to deal with cheating on WII, i.e. by banning the hackers, the Nintendo Tech Support Forum suggests that you fill out an online customer service form so Nintendo can investigate. Fill out all the pertinent information that you can remember about the match such as method of cheating and the player's name. A link to the form is available in the Resources section.