call your secretary of state or look at their website... it should say on there as well as give all the other laws involving mopeds... like here it is illegal to ride double, a moped is classified as a 2 or 3 wheeled vehicle that is 50ccs or lower that does not get more than 30 mph.... but these laws seem to be being broken as most newer peds that are getting registered go 35 to 40......
oh and you cant ride on the sidewalk :P
thats just here in michigan, but it should all the information for you on the website.