Well its not just for going faster than 20 but what that means legally according to some overzealous law enforcement folk. Basically, if you go faster than 20 mph some cops classify you as a moped and are taking it upon themselves to write tickets for driving without insurance or registration. In some cases they can even write an additional ticket for driving with no license if you don't have a driver's license. Even though the MVD won't register these bikes and no insurance agent will insure them, the law doesn't lay down a penalty for exceeding the 20 mph speed limit so it kind of leaves it open for cops to write all of the tickets if they are so inclined. Just be careful.