31 CFR § 515.302 - National.
(a) The term national when used with respect to a country shall include:
(1) A subject or citizen of that country or any person who has been domiciled in or a permanent resident of that country at any time on or since the “effective date,” except persons who were permanent residents of or domiciled in that country in the service of the U.S. Government and persons whose transactions in that country were authorized by the Office of Foreign Assets Control.
(2) Any partnership, association, corporation, or other organization that, on or since the effective date:
(i) Was or has been organized under the laws of that country;
(ii) Had or has had its principal place of business in that country; or
(iii) Was or has been controlled by, or a substantial part of the stocks, share, bonds, debentures, notes, drafts, or other securities or obligations of which was or has been controlled by, directly or indirectly, that country and/or one or more nationals thereof.
(3) Any organization's office or other sub-unit that is located within that country.
(4) Any person to the extent that such person, on or since the “effective date” was or has been acting or purporting to act directly or indirectly for the benefit or on behalf of any national of that country.
(5) Any other person who there is reasonable cause to believe is a “national” as defined in this section.
(b) Persons who travel in Cuba do not become nationals of Cuba solely because of such travel.
(c) The Secretary of the Treasury retains full power to determine that any person is or shall be deemed to be a “national” within the meaning of this section, and to specify the foreign country of which such person is or shall be deemed to be a national.