The state of
Maryland, never a state to miss the opportunity to tax the peasants, passed a law that requires that mopeds and motor scooters be registered and display a sticker. In addition, you must have a "Moped operator's permit"
After a quick Google search, I found out that rules vary widely around the country.
The great state of
Texas requires a special license and a tag be purchased.
In
South Carolina, registration is not required, but a special endorsement on your license is required.
All of this being said, states respect other states DMV requirements. But only after stopping you will a LEO know that you are from NC and let you off. Plus, many private CGs don't allow you to ride them on their properties. Might not be as good of idea as you thought.
ON EDIT: As a side note,
DMV.org is a pretty useful website to find out rules and regs for all states on a variety of motor vehicle issues.