Geneva Protocol
El Salvador, the final signatory to ratify the Protocol, did so on 26 February 2008. As of April 2021, 146 states have ratified, acceded to, or succeeded to the Protocol, most recently Colombia on 24 November 2015.

Reservations: A number of countries submitted reservations when becoming parties to the Geneva Protocol, declaring that they only regarded the non-use obligations as applying with respect to other parties to the Protocol and/or that these obligations would cease to apply with respect to any state, or its allies, which used the prohibited weapons. Several Arab states also declared that their ratification did not constitute recognition of, or diplomatic relations with, Israel, or that the provision of the Protocol were not binding with respect to Israel.
Generally, reservations not only modify treaty provisions for the reserving party, but also symmetrically modify the provisions for previously ratifying parties in dealing with the reserving party.: 394   Subsequently, numerous states have withdrawn their reservations, including the former Czechoslovakia in 1990 prior to its dissolution, or the Russian reservation on biological weapons that "preserved the right to retaliate in kind if attacked" with them, which was dissolved by President Yeltsin.
According to the Vienna Convention on Succession of States in respect of Treaties, states which succeed to a treaty after gaining independence from a state party "shall be considered as maintaining any reservation to that treaty which was applicable at the date of the succession of States in respect of the territory to which the succession of States relates unless, when making the notification of succession, it expresses a contrary intention or formulates a reservation which relates to the same subject matter as that reservation."  While some states have explicitly either retained or renounced their reservations inherited on succession, states which have not clarified their position on their inherited reservations are listed as "implicit" reservations.

 

Reservations

Notes

Non-signatory states: The remaining UN member states and UN observers that have not acceded or succeeded to the Protocol are:

Chemical weapons prohibitions: 

References: 

Further reading: Frederic Joseph Brown (2005). "Chapter 3: The Evolution of Policy 1922-1939 / Geneva Gas Protocol". Chemical warfare: a study in restraints. Transaction Publishers. pp. 98–110. ISBN 1-4128-0495-7.
Bunn, George. "Gas and germ warfare: international legal history and present status." Proceedings of the National Academy of Sciences of the United States of America 65.1 (1970): 253+. online
Webster, Andrew. "Making Disarmament Work: The implementation of the international disarmament provisions in the League of Nations Covenant, 1919–1925." Diplomacy and Statecraft 16.3 (2005): 551–569.

External links: 
The text of the protocol Archived 7 September 2013 at the Wayback Machine
Weapons of War: Poison Gas