40 CFR §1090.230

1. (a)No person may sell, introduce, cause, or permit the sale or introduction of gasoline containing greater than 10 volume percent ethanol (e.g., E15) into any model year 2000 or older light-duty gasoline motor vehicle, any heavy-duty gasoline motor vehicle or engine, any highway or off-highway motorcycle, or any gasoline-powered nonroad engine, vehicle, or equipment.
2. (b)Paragraph (a) of this section does not prohibit a person from producing, selling, introducing, causing, or allowing the sale or introduction of gasoline containing greater than 10 volume percent ethanol into any flex-fuel vehicle or flex-fuel engine.