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. 13.
Art. 13. Individuals who follow an army without directly belonging to it, such as newspaper correspondents and reporters, sutlers and contractors, who fall into the enemy's hands and whom the latter thinks expedient to detain, are entitled to be treated as prisoners of war, provided they are in possession of a certificate from the military authorities of the army which they were accompanying.