The state of Alabama does not require titling or registration of most ATVs through the DMV because they're "generally not manufactured to comply with federal and state statutes." In order to determine whether an ATV needs to be registered, a license plate issuing official needs to inspect it to see if it complies with all the applicable state and federal laws. However, an ATV owner can register their ATV with the Alabama State Law Enforcement Agency by visiting any state boat licensing agent. Registration is renewable every three years. ATVs purchased from dealers will be registered by the dealer.
Check out these Gordon, AL ATV/OHV resources: