Except as provided in subsection (b)(2) of this section, the President shall impose the sanction described in subsection (c) of this section if the President determines in writing that, on or after the effective date of this subchapter, a foreign person or a United States person has materially and with requisite knowledge contributed, through the export from the United States or any other country of any goods or technology (as defined in section
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(2) of this title), to the efforts by any individual, group, or non-nuclear-weapon state to acquire unsafeguarded special nuclear material or to use, develop, produce, stockpile, or otherwise acquire any nuclear explosive device.