II. The Prohibitory Scope of the Geneva Protocol of 1925
The Protocol for the Prohibition of the Use in War of Asphyxiating, Poisonous or Other Gases, and of Bacteriological Methods of Warfare was signed at Geneva on June 17, 1925. It has been formally ratified by or is otherwise binding upon eighty-four nations, including all the major military and industrial nations of the world except the United States and Japan. Although the United States Government participated in the drafting of the Geneva Protocol and signed it, the Senate failed to give its consent to the ratification of the treaty.
The Geneva Protocol prohibits two things: (a) “the use in war of asphyxiating, poisonous or other gases, and of all analogous liquids, materials or devices,” and (b) “the use of bacteriological methods of warfare.” It does not prohibit the production, acquisition, or stockpiling of these weapons, nor does it apply to their use for purposes other than in “war.” This means, among other things, that the testing of these weapons is not proscribed by the Geneva Protocol; the same is true of the manufacture of equipment capable of dispersing them.
The major question that has arisen with regard to the interpretation of the Protocol is whether irritant chemicals (tear gas) and anti-plant chemicals fall within the prohibition of the use in war of “asphyxiating, poisonous or other gases.” Before that question can be answered, we must be clear about the manner in which the meaning of a doubtful passage in a treaty is determined.
Treaties are to be interpreted “in accordance with the ordinary meaning to be given to the terms of the treaty in their context and in the light of its object and purpose.” There may also be taken into account the subsequent practice of the parties establishing their agreement on its interpretation. And if the meaning of the agreement is still ambiguous or obscure, one may turn to the preparatory work of the treaty and the circumstances of its conclusion.
It is important to notice in this connection that it is the subsequent practice of the parties that may be taken into account. This suggests that the interpretation attached to the Protocol by the United States, a non-party, carries much less weight than some have assumed. A certain amount of confusion has been occasioned by a failure to distinguish evidence that goes to the interpretation of the Protocol from evidence of the state of customary international law. The reach of the treaty prohibition of chemical warfare is not necessarily coextensive with the corresponding prohibition found in customary international law. In other words, it may well be that the Geneva Protocol—the treaty or conventional prohibition—outlaws all forms of chemical warfare, including irritant chemicals and anti-plant chemicals.
This does not mean, however, that as sweeping a prohibition need necessarily have passed into customary international law as a rule binding on all states, whether or not parties to the Protocol.
Unless one recognizes that the reach of the conventional and the customary international law rules need not be identical, it is impossible to determine from the available negotiating history and subsequent practice what forms of chemical warfare the Geneva Protocol was intended to outlaw. For what might be regarded as legally conclusive evidence to support a sweeping interpretation of the Geneva Protocol can, and in fact does, become much less conclusive for the purpose of ascertaining the full scope of the customary rule. Thus, although the chemical warfare practice and declarations of states not parties to the Geneva Protocol are relevant evidence for the purpose of delimiting the scope of the customary rule, they do not bear witness to the scope of the conventional rule. If one is guided by this principle in analyzing the chemical warfare prohibition of the Geneva Protocol, many of the doubts regarding its intended scope disappear.
-  For the official French and English texts of the Geneva Protocol, see 94 L.N. Treaty Series 65 (1929).
-  These statistics have been supplied by the United States Department of State and include statesthat are bound by the Protocol by virtue of its ratification by governments which they succeeded.
-  The Geneva Protocol was drafted at the Conference on International Trade in Arms, which wasconvened by the League of Nations and met in Geneva from May 4 through June 17, 1925. For theofficial records of this conference, see League of Nations, Proceedings of the Conference for theSupervision of the International Trade in Arms and Ammunition and in Implements of War (1925),hereinafter cited as 1925 Geneva Conference Proceedings.
-  The Geneva Protocol was transmitted to the U. S. Senate for its advice and consent on Jan. 12,1926. It was not put to a vote because the unexpected opposition to it that had developed promptedthe Chairman of the Foreign Relations Committee (Senator William Borah) to have the Protocolreferred back to his Committee. This was done on Dec. 13, 1926. See 68 Cong. Rec. 368 (1927). Itwas not reported out of that Committee again and was among a number of treaties that werewithdrawn by President Truman in 1947 “with a view to placing the treaty calendar on a currentbasis.” 16 Dept. of State Bulletin 726 (1947).
-  Convention on the Law of Treaties, opened for signature at Vienna, May 23, 1969, Art. 31,par. 1. U.N. Doc. A/CONF.39/27 (1969); 63 A.J.I.L. 875 (1969).
-  Art. 31, par. 3(b).
-  Art. 32 describes recourse to the travaux preparatoires as “supplementary means of interpretation.”