; Department of Justice buy-back program (a) In general Section 501(a)(1) of title I of the Omnibus Crime Control and Safe Streets Act of 1968 ( 34 U.S.C. 10152(a)(1) ), as amended by section 515 of this Act, is amended by adding at the end the following: (K) Compensation for surrendered firearm silencers and firearm mufflers, as those terms are defined in section 921 of title 18, United States Code, under buy-back programs for firearm silencers and firearm mufflers. . (b) Requirement During the 90-day period described in section 525, the Attorney General shall establish and implement a buy-back program, to be carried out across the United States, to purchase firearm silencers and firearm mufflers (as defined in section 921(a) of title 18, United States Code) from individuals seeking to comply with the requirements of this subtitle and the amendments made by this subtitle. 525. Effective date The amendments made by this subtitle shall take effect on the date that is 90 days after the date of enactment of this Act. VI Firearm trafficking 601. Prohibition against multiple firearm sales or purchases (a) Prohibition Section 922 of title 18, United States Code, as amended by section 522 of this Act, is amended by adding at the end the following: (ff) Prohibition against multiple firearm sales or purchases (1) Sale It shall be unlawful to sell, transfer, or otherwise dispose of a firearm, in of affecting interstate or foreign commerce, to any person who is not licensed under section 923 knowing or having reasonable cause to believe that such person purchased a firearm during the 30-day period ending on the date of such sale or disposition. (2) Purchase It shall be unlawful for any person who is not licensed under section 923 to purchase more than 1 firearm that has been shipped or transported in interstate or foreign commerce during any 30-day period. (3) Exceptions Paragraphs (1) and (2) shall not apply to— (A) a lawful exchange of 1 firearm for 1 firearm