Treaty of Bern (1968)
“ The right of transit is guaranteed throughout the entire territory of the Union. Consequently, there shall be full and entire liberty of exchange, the several Postal Administrations of the Union being able to send reciprocally, in transit through intermediate countries, closed mails as well as correspondence in open mails, according to the requirements of trade and the exigencies of the postal service. Closed mails and correspondence sent in open mails must always be forwarded by the most rapid routes at the command of the Postal Administrations concerned. ”
