; or (C) a semiautomatic firearm that has been modified in any way that— (i) materially increases the rate of fire of the firearm; or (ii) approximates the action or rate of fire of a machinegun. (2) Except as provided in paragraph (3), not later than 120 days after the date of enactment of this subsection, any person who lawfully owns or possesses a semiautomatic firearm that was modified as described in paragraph (1)(C) before such date of enactment shall register the semiautomatic firearm in accordance with section 5841 of the Internal Revenue Code of 1986. (3) This subsection does not apply with respect to the importation for, manufacture for, sale to, transfer to, or possession by or under the authority of, the United States or any department or agency thereof or a State, or a department, agency, or political subdivision thereof. (4) Paragraph (1) shall not apply to any lawful transfer or possession of a semiautomatic firearm described in paragraph (1)(C) that— (A) was lawfully modified and possessed before the date of enactment of this subsection; and (B) is registered in accordance with paragraph (2). ; and (3) in section 924(a)(2), by striking , or (o) and inserting (o), or (v) . (b) Amendment to the National Firearms Act Section 5845(a) of the Internal Revenue Code of 1986 is amended by striking and (8) a destructive device and inserting (8) a destructive device; and (9) a semiautomatic firearm, as defined in section 921 of title 18, United States Code, that is subject to the prohibition under section 922(v)(1)(C) of such title 18 .