Related Rule
Finland
Practice Relating to Rule 137. Participation of Child Soldiers in Hostilities
Finland’s Criminal Code (1889), as amended in 2008, provides that any person who “takes or recruits children below the age of 18 years into military forces or into groups in which they are used in hostilities” 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)(5).
(emphasis in original)
At the 27th International Conference of the Red Cross and Red Crescent in 1999, Finland pledged “to promote the adoption of national and international standards prohibiting the military … participation in armed conflicts of persons under 18 years of age”. 
Finland, Pledge made at the 27th International Conference of the Red Cross and Red Crescent, Geneva, 31 October–6 November 1999.
In 2003, in its fifth periodic report to the Human Rights Committee, Finland stated: “The Optional Protocol to the Convention on the Rights of the Child on the involvement of children in armed conflict entered into force for Finland on 1 July 1997.” 
Finland, Fifth periodic report to the Human Rights Committee, 24 July 2003, UN Doc. CCPR/C/FIN/2003/5, submitted 17 June 2003, § 331.