Finland
Practice Relating to the Use of Prohibited Weapons
Under Finland’s Revised Penal Code (1995), any person who, in time of war, “uses a prohibited means of warfare or weapon [or] otherwise violates the provisions of an international agreement on warfare binding on Finland or the generally acknowledged and established rules and customs of war under public international law” shall be punished for war crime. 
Finland, Revised Penal Code, 1995, Chapter 11, Section 1(1)(1) and (3).
Finland’s Criminal Code (1889), as amended in 2008, provides that any person who “uses … weapons, ammunition or materiel that cause excessive injuries or unnecessary suffering … or other prohibited weapons or ordnance” shall be “sentenced for a war crime to imprisonment for at least one year or for life”. 
Finland, Criminal Code, 1889, as amended in 2008, Chapter 11, Section 5(1)(14).
(emphasis in original)