The Department of Justice proposes amending Bureau of Alcohol, Tobacco, Firearms, and Explosives (ATF) regulations to clarify definitions of two categories of persons who are prohibited from receiving, possessing, shipping, or transporting firearms under the Gun Control Act of 1968. The proposed rule would clarify that the statutory term ‘‘adjudicated as a mental defective’’ includes persons who are found incompetent to stand trial or not guilty by reason of mental disease or defect, lack of mental responsibility, or insanity, and that the term includes persons found guilty but mentally ill.