(a) Any authority granted to the President by section 1702 of
this title may be exercised to deal with any unusual and
extraordinary threat, which has its source in whole or substantial
part outside the United States, to the national security, foreign
policy, or economy of the United States, if the President declares
a national emergency with respect to such threat.
(b) The authorities granted to the President by section 1702 of
this title may only be exercised to deal with an unusual and
extraordinary threat with respect to which a national emergency has
been declared for purposes of this chapter and may not be exercised
for any other purpose. Any exercise of such authorities to deal
with any new threat shall be based on a new declaration of national
emergency which must be with respect to such threat.