Viet Nam
Practice Relating to the Use of Prohibited Weapons
Viet Nam’s Penal Code (1990) punishes “anyone who, in time of war, … uses prohibited means or methods of warfare”. 
Viet Nam, Penal Code, 1990, Article 279.
Viet Nam’s Penal Code (1999) provides for the punishment of those “who, in time of peace or time of war, undertake … the use of prohibited means or methods of warfare”. 
Viet Nam, Penal Code, 1999, § 343.
Viet Nam’s Criminal Code (2015) states:
Article 423. War crimes
1. Any person in wartime who orders or directly commits the murder of civilians, wounded people, or prisoner[s] of war[]; pillages; destroys residential areas; uses banned war instruments or methods[;] or commits other acts that seriously violate international law or an international agreement to which [the] Socialist Republic of Vietnam is a signatory shall face a penalty of 10–20 years’ imprisonment, life imprisonment, or death
2. [If t]his offence is committed under pressure or order[s] given by superior officers, the offender shall face a penalty of 10–20 years’ imprisonment. 
Viet Nam, Criminal Code, 2015, Article 423.