Annex to the Convention: Regulations respecting the laws and customs of war on land - Section I : On belligerents - Chapter II : Prisoners of war - Regulations: Art. 16.
Art. 16. Inquiry offices enjoy the privilege of free postage. Letters, money orders, and valuables, as well as parcels by post, intended for prisoners of war, or dispatched by them, shall be exempt from all postal duties in the countries of origin and destination, as well as in the countries they pass through.
Presents and relief in kind for prisoners of war shall be admitted free of all import or other duties, as well as of payments for carriage by the State railways.