There are ever more rules and regulations regarding ATV safety including the required safety equipment like helmets, gloves and riding boots, age requirements, licensing, sound levels and safety training.
Then there's legal requirements to own and operate an ATV on public land and roads. You need to have a title (proof of ownership) and registration (annual fees paid to ride on public land).
Below is a state-by-state listing of the most current ATV laws by state:Alabama
ATV registration and titling laws updated regularly. Check with your state's Bureau of Motor Vehicles (Department of Motor Vehicles / Department of Transportation). From there, you may need to search for ATV, all-terrain vehicle, OHV or off-highway vehicle to get to the information about quads. (If you know of a recent update in your state, please let me know.)