Related Rule
Denmark
Practice Relating to Rule 136. Recruitment of Child Soldiers
Denmark’s Military Criminal Code (1973), as amended in 1978, provides:
Any person who uses war instruments or procedures the application of which violates an international agreement entered into by Denmark or the general rules of international law, shall be liable to the same penalty [i.e. a fine, lenient imprisonment or up to 12 years’ imprisonment]. 
Denmark, Military Criminal Code, 1973, as amended in 1978, § 25(1).
Denmark’s Military Criminal Code (2005) provides:
Any person who deliberately uses war means [“krigsmiddel”] or procedures the application of which violates an international agreement entered into by Denmark or international customary law, shall be liable to the same penalty [i.e. imprisonment up to life imprisonment]. 
Denmark, Military Criminal Code, 2005, § 36(2).
At the 27th International Conference of the Red Cross and Red Crescent in 1999, Denmark pledged “to promote the adoption of national and international standards prohibiting the military recruitment … in armed conflicts of persons under 18 years of age”. 
Denmark, Pledge made at the 27th International Conference of the Red Cross and Red Crescent, Geneva, 31 October–6 November 1999.
In 2008, in its fourth periodic report to the Committee on the Rights of the Child, Denmark stated:
586. As indicated by the declaration issued by the Ministry of Foreign Affairs on 13 August 2002, it is not possible under Danish law to let personnel below 18 years of age perform military service in the National Defence. In May 1998, the Minister of Defence made the decision that the age limit for military service in the National Defence had to be raised to 18 years.
590. In June 2006, the Defence Personnel Act was amended and in connection with the amendments the 18-year minimum age for military service in the Defence was laid down by law and a new provision in section 2 (3) of the Act prescribed that no one may be hired or called up for military service until they have attained the age of 18 years. The amendments entered into force on 1 July 2006 and the Act on Defence Personnel was promulgated by Consolidation Act No. 667 of 20 June 2006.
595. The Danish military authorities and the Ministry of Defence are responsible for complying with the rules on a minimum age limit of 18 years for military service in the National Defence. 
Denmark, Fourth periodic report to the Committee on the Rights of the Child, 22 January 2010, UN Doc. CRC/C/DNK/4, submitted 19 August 2008, §§ 586, 590 and 595.
In 2009, in a statement on “Children and Armed Conflict” made before the UN Security Council on behalf of Denmark, Finland, Iceland, Norway and Sweden, the permanent representative of Finland stated:
Recruitment of boys and girls to take part in hostilities is a violation of international law, and a war crime in both international and non-international armed conflicts. The (nearly) universal recognition of the prohibition on recruiting or using child soldiers must be matched by effective implementation on the domestic level. The first case before the International Criminal Court (ICC) to have proceeded to trial phase, the one against Thomas Lubanga Dyilo, is a milestone in the efforts to end impunity for the use of child soldiers. …
The Nordic countries wish to emphasize the need for all parties to relevant situations of armed conflict to present concrete, time-bound action plans with detailed descriptions on how they will end and prevent the recruitment of child soldiers …
[W]e would like to reiterate our encouragement to the SC [Security Council] and to the entire UN system to give children in armed conflict the attention they deserve. 
Denmark, Statement by the permanent representative of Finland before the UN Security Council on “Children and Armed Conflict” made on behalf of Denmark, Finland, Iceland, Norway and Sweden, 29 April 2009.