Counties shall have the option to allow all-terrain vehicles and snowmobiles over one thousand (1,000) pounds unladen gross weight, if numbered as a snowmobile, to use snowmobile trails in the county. No other vehicles shall operate on groomed snowmobile trails unless specifically allowed by the county. Any all-terrain vehicle and snowmobile over one thousand (1,000) pounds unladen gross weight operating on groomed snowmobile trails during the winter snowmobiling season when the trails are groomed shall be numbered as a snowmobile under the provisions of section 67-7103, Idaho Code. Violation of the provisions of this section shall be an infraction.