It shall be unlawful, except as provided in section 2121 of this title, for any person, inside or outside of the United States, to knowingly participate in the development of, manufacture, produce, transfer, acquire, receive, possess, import, export, or use, or possess and threaten to use, any atomic weapon. Nothing in this section shall be deemed to modify the provisions of section 2051(a) or 2131 of this title.