I am seeking legal advice from a local attorney, I'm just reaching out to forum and trying to get more information. Some states do require registration/insurance of ATVs, North Carolina is not one of them.I am afraid what the sheriff told you is not entirely true as some ATVs are considered motor vehicles and must be registered with your state and insured.
The specifics matter here so, as advised earlier more than once, you would be smart to seek out assistance from an attorney in your area prior to pursuing a legal action. Your license and your criminal record could be affected If you move ahead without this personal consultation.
Good luck.
It also kind of makes sense, all the motor vehicles listed that are prohibited to be pawned (Mobile Home, RV, or Car other than a motorcycle) ALL require title, registration and insurance. ATV does not