Yugoslavia, Socialist Federal Republic of
Practice Relating to the Use of Prohibited Weapons
Under the Socialist Federal Republic of Yugoslavia’s Penal Code (1976), as amended in 2001, the use of, or the order to use, “means or methods of combat prohibited under the rules of international law, during a war or an armed conflict” is a war crime. 
Yugoslavia, Socialist Federal Republic of, Penal Code, 1976, as amended in 2001, Article 148(1).
At the CDDH, the Socialist Federal Republic of Yugoslavia voted in favour of the Philippine proposal concerning an amendment to include “the use of weapons prohibited by international Convention, namely: … asphyxiating, poisonous or other gases, and all analogous liquids, materials or devices” in the list of grave breaches in Article 74 of the draft Additional Protocol I (now Article 85). 
See Philippines, Proposal of amendment to Article 74 of the draft Additional Protocol I submitted to the CDDH, Official Records, Vol. III, CDDH/418, 26 May 1977, p. 322.
However, because that amendment had been rejected the Socialist Federal Republic of Yugoslavia stated that it
deeply regrets that the use of unlawful methods or means of combat was not included in the grave breaches, particularly since to have done so would merely have been to have codified an already existing rule of customary law, because there can be no doubt that to use prohibited weapons or unlawful methods of making war is already to act unlawfully, that is, it is a war crime punishable by existing international law. 
Yugoslavia, Socialist Federal Republic of, Statement at the CDDH, Official Records, Vol. VI, CDDH/SR.44, 30 May 1977, p. 306.