The Optional Protocol to the Convention on the Rights of the Child on the Involvement of Children in Armed Conflict (OPAC), also known as the child soldier treaty, is a multilateral treaty whereby states agree to: 1) prohibit the conscription into the military of children under the age of 18; 2) ensure that military recruits are no younger than 16; and 3) prevent recruits aged 16 or 17 from taking a direct part in hostilities.

The United Nations General Assembly adopted the treaty as a supplementary protocol to the Convention on the Rights of the Child by resolution 54/263 on 25 May 2000.

[4] In World War II, child soldiers fought throughout Europe, in the Warsaw Uprising,[5] in the Jewish resistance,[6] and in the Soviet Army.

[12] In addition, the Protocols did not prohibit belligerents from using children younger than 15 in hostilities when their participation was not "direct"; for example, as scouts, porters, informants, spies, message-carriers and in other support roles.

While the large majority of states negotiating the protocol were willing to end all military recruitment of children under the age of 18 (the so-called "straight-18" principle), a small number were opposed: Bangladesh, Cuba, Israel, South Korea, Kuwait, Pakistan, the United Kingdom (UK) and the United States (US).

[13] The study was proposed by the Committee on the Rights of the Child, commissioned by the UN General Assembly, and produced by Graça Machel in 1996: Impact of armed conflict on children.

[8] The Coalition worked in alliance with a small group of states actively advocating for the straight-18 principle internationally: Canada, Denmark, Ethiopia, Finland, Japan, Mozambique, Norway, Portugal, South Africa, Sweden, and Switzerland.

[20] The meeting, co-sponsored by Child Soldiers International, UNICEF, and the governments of Belgium, Canada, Colombia, France and Sierra Leone, was attended by approximately 100 delegates.

The Special Representative of the UN Secretary-General for Children and Armed Conflict, Virginia Gamba, reported on the progress made and still to be achieved since the treaty was adopted: We have really come a long way.

Making sure all boys and girls released and their communities have access to meaningful reintegration – to help them overcome the harrowing experiences they have been through – is essential.

But this remains a huge challenge.The main obligations of the OPAC treaty are as follows:[21] Other provisions of the treaty include the following: The sentence "States Parties shall take all feasible measures to ensure that members of their armed forces who have not attained the age of 18 years do not take a direct part in hostilities" was adapted from 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, with an alteration from fifteen years to eighteen years and some other minor modifications.

[23][24] On ratification of the treaty, the UK's binding declaration stated its understanding that, while it would endeavour not to use child recruits in hostilities, the protocol "would not exclude the deployment of members of its armed forces under the age of 18 to take a direct part in hostilities where: a) there is a genuine military need to deploy their unit or ship to an area in which hostilities are taking place; and b) by reason of the nature and urgency of the situation:– i) it is not practicable to withdraw such persons before deployment; or ii) to do so would undermine the operational effectiveness of their ship or unit, and thereby put at risk the successful completion of the military mission and/or the safety of other personnel.

[26] The Committee on the Rights of the Child has urged the UK to alter its policy so as to ensure that children cannot take part in hostilities under any circumstances.