§ 602. Foreign letters out of the mails

• (a) Except as provided in section 601 of this title , the master of a vessel departing from the United States for foreign ports may not receive on board or transport any letter which originated in the United States that—
  • (1) has not been regularly received from a United States post office; or
  • (2) does not relate to the cargo of the vessel.
• (b) The officer of the port empowered to grant clearances shall require from the master of such a vessel, as a condition of clearance, an oath that he does not have under his care or control, and will not receive or transport, any letter contrary to the provisions of this section.
• (c) Except as provided in section 1699 of title 18 , the master of a vessel arriving at a port of the United States carrying letters not regularly in the mails shall deposit them in the post office at the port of arrival.