Transportation of mail of adjoining countries through the United States

§ 6103. Transportation of mail of adjoining countries through the United States The Postmaster General, by and with the advice and consent of the President, may make arrangements to allow the mail of countries adjoining the United States to be transported over the territory of the United States from one point in that country to any other point therein, at the expense of the country to which the mail belongs, upon obtaining a like privilege for the transportation of the United States mail through the country to which the privilege is granted. The President or Congress may annul the privilege at any time. The privilege shall terminate one month succeeding the day on which notice of the act of the President or Congress is given to the chief executive or head of the post office department of the country whose privilege is to be annulled.