(a) As used in this section, "secret of state" means information not open or theretofore officially disclosed to the public involving the public security or concerning the military or naval organization or plans of the United States, or a state or territory, or concerning international relations.
(b) A witness has a privilege to refuse to disclose a matter on the ground that it is a secret of state, and evidence of the matter is inadmissible, (1) if the judge finds that the matter is a secret of state, or (2) unless the chief officer of the department of government administering the subject matter which the secret concerns has consented that it be disclosed in the action.