Treaties, States Parties and Commentaries
Treaties and Documents
Geneva Conventions of 1949 and Additional Protocols, and their Commentaries
Historical Treaties and Documents
Rules concerning the Control of Wireless Telegraphy in Time of War and Air Warfare. Drafted by a Commission of Jurists at the Hague, December 1922 - February 1923.
Part II: Rules of Air Warfare#Chapter III: Belligerents. - Art. 16.
Art. 16. No aircraft other than a belligerent military aircraft may take part in hostilities in any form whatever.
The term "hostilities" includes the transmission, during a flight, of military information for the immediate use of a belligerent.
No private aircraft may be armed in time of war outside the jurisdiction of its own country.