42 U.S.C. § 2160c

(a) In addition to other applicable requirements— (1) a license may be issued by the Nuclear Regulatory Commission under this chapter for the export of special nuclear material described in subsection (b); and (2) approval may be granted by the Secretary of Energy under section 2160 of this title for the transfer of special nuclear material described in subsection (b); only after the Secretary of Defense has been consulted on whether the physical protection of that material during the export or transfer will be adequate to deter theft, sabotage, and other acts of international terrorism which would result in the diversion of that material. If, in the view of the Secretary of Defense based on all available intelligence information, the export or transfer might be subject to a genuine terrorist threat, the Secretary shall provide to the Nuclear Regulatory Commission or the Secretary of Energy, as appropriate, his written assessment of the risk and a description of the actions the Secretary of Defense considers necessary to upgrade physical protection measures. (b) Subsection (a) applies to the export or transfer of more than 2 kilograms of plutonium or more than 5 kilograms of uranium enriched to more than 20 percent in the isotope 233 or the isotope 235.