According to Article 77.2 of the Additional Protocol I to the Geneva Conventions of 12 August 1949, and relating to the Protection of Victims of International Armed Conflicts, adopted in 1977:

The Parties to the conflict shall take all feasible measures in order that children who have not attained the age of fifteen years do not take a direct part in hostilities and, in particular, they shall refrain from recruiting them into their armed forces. In recruiting among those persons who have attained the age of fifteen years but who have not attained the age of eighteen years, the Parties to the conflict shall endeavour to give priority to those who are oldest.

As the ICRC commentary on Protocol I makes clear, this is not a complete ban on the use of children in conflict. The ICRC had suggested that the Parties to the conflict should “take all necessary measures”, which became in the final text, “take all feasible measures” which is not a total prohibition on their doing so because feasible should be understood as meaning “capable of being done, accomplished or carried out, possible or practicable”. Refraining from recruiting children under fifteen does not exclude child who volunteer for armed service. During the negotiations over the clause “take a part in hostilities” the word “direct” was added to it, this opens up the possibility that child volunteers could be involved indirectly in hostilities, gathering and transmitting military information, helping in the transportation of arms and munitions, provision of supplies etc.[12]

Article 4.3.c of Protocol II, additional to the Geneva Conventions of 12 August 1949, and relating to the Protection of Victims of Non-International Armed Conflicts, adopted in 1977, states “children who have not attained the age of fifteen years shall neither be recruited in the armed forces or groups nor allowed to take part in hostilities”.

[edit] International labour law

Forced or compulsory recruitment of children for use in armed conflict, is one of the predefined worst forms of child labour in terms of the International Labour Organisation’s Worst Forms of Child Labour Convention, 1999, adopted in 1999.

In terms of the Worst Forms of Child Labour Recommendation ratifying countries should ensure that forced or compulsory recruitment of children for use in armed conflict is a criminal offence, and also provide for other criminal, civil or administrative remedies to ensure the effective enforcement of such national legislation (Article III(12) to (14)).