The Protocol for the Prohibition of the Use in War of Asphyxiating, Poisonous or other Gases, and of Bacteriological Methods of Warfare, usually called the Geneva Protocol, is a treaty prohibiting the first use of chemical and biological weapons in international armed conflicts. It was signed at Geneva on 17 June 1925 and entered into force on 8 February 1928. It was registered in League of Nations Treaty Series on 7 September 1929. The Geneva Protocol is a protocol to the Hague Conventions of 1899 and 1907.
It prohibits the use of "asphyxiating, poisonous or other gases, and of all analogous liquids, materials or devices" and "bacteriological methods of warfare". This is now understood to be a general prohibition on chemical weapons and biological weapons, but has nothing to say about production, storage or transfer. Later treaties did cover these aspects — the 1972 Biological Weapons Convention (BWC) and the 1993 Chemical Weapons Convention (CWC).
A number of countries submitted reservations when becoming parties to the Geneva Protocol, declaring that they only regarded the non-use obligations as applying to other parties and that these obligations would cease to apply if the prohibited weapons were used against them.
The main elements of the protocol are now considered by many to be part of customary international law.