Rule 120. Accommodation for Children Deprived of Their Liberty
Rule 120. Children who are deprived of their liberty must be held in quarters separate from those of adults, except where families are accommodated as family units.
Summary
State practice establishes this rule as a norm of customary international law applicable in both international and non-international armed conflicts.
International armed conflicts
The Fourth Geneva Convention provides that interned children must be lodged together with their parents, except when separation of a temporary nature is necessitated for reasons of employment or health or for the purpose of enforcement of penal or disciplinary sanctions.[1]  This rule is contained in Additional Protocol I.[2]  The Convention on the Rights of the Child, which has been almost universally ratified, specifies this requirement.[3]  In addition, the International Covenant on Civil and Political Rights requires that juveniles in detention be separated from adults.[4] 
Several military manuals set forth the requirement to separate children from adults while in detention, unless they are accommodated with their families.[5]  This requirement is also contained in the legislation of a number of States.[6] 
Non-international armed conflicts
The requirement to house child and adult detainees separately is set forth in the International Covenant on Civil and Political Rights and in the Convention on the Rights of the Child, the latter ratified almost universally.[7]  In addition, it is provided for in many other instruments pertaining also to non-international armed conflicts.[8] 
This rule is contained in some military manuals which are applicable in non-international armed conflicts.[9]  The legislation and other regulations of several States require respect for this rule.[10]  In 1993, Peru and the Philippines informed the UN Committee on the Rights of the Child that they required that detained children be separated from adults.[11] 
No official contrary practice was found with respect to either international or non-international armed conflicts.
Interpretation
As the rule indicates, children must only be separated from adults to the extent that this does not involve a violation of the right of families to be housed together. Additional Protocol I, the UN Secretary-General’s Bulletin on observance by United Nations forces of international humanitarian law and the Rules for the Protection of Juveniles Deprived of their Liberty formulate the exception in terms of keeping members of the same family together.[12]  The Convention on the Rights of the Child, meanwhile, formulates the exception in terms of what is required by the “best interests of the child”.[13] 
Upon ratification of the Convention on the Rights of the Child, Australia reserved the right not to detain children separately where this would be inconsistent with “the obligation that children be able to maintain contact with their families”.[14]  Canada, New Zealand and the United Kingdom made similar statements upon ratification of the Convention (providing for an exception where separation would not be “appropriate” or mixing would be “mutually beneficial”).[15] 
The rule that members of the same family must be housed together is supported by the requirement to respect family life (see Rule 105).
Collected practice does not uniformly point to an age limit to determine what constitutes a child under this rule. Additional Protocol I leaves the issue open but suggests that 15 is the absolute minimum.[16]  The Convention on the Rights of the Child defines a child as “every human being below the age of eighteen years unless, under the law applicable to the child, majority is attained earlier”.[17]  This divergence is also reflected in national legislation, for example, Rwanda’s Prison Order requires that prisoners under the age of 18 be held separately, while Pakistan’s Prisons Act requires such a measure for prisoners under the age of 21.[18] 

[1] Fourth Geneva Convention, Article 82, second paragraph (cited in Vol. II, Ch. 37, § 146).
[2] Additional Protocol I, Article 77(4) (adopted by consensus) (ibid., § 148).
[3] Convention on the Rights of the Child, Article 37(c) (ibid., § 149).
[4] International Covenant on Civil and Political Rights, Article 10 (ibid., § 147).
[5] See, e.g., the military manuals of Argentina (ibid., §§ 164–165), Australia (ibid., § 166), Cameroon (ibid., § 167), Canada (ibid., § 168), Germany (ibid., § 169), Spain (ibid., § 170), United Kingdom (ibid., § 171) and United States (ibid., § 172).
[6] See, e.g., the legislation of Bangladesh (ibid., § 173), Ireland (ibid., § 174), Nicaragua (ibid., § 175), Norway (ibid., § 176), Pakistan (ibid., § 177), Philippines (ibid., § 178) and Rwanda (ibid., §§ 179).
[7] International Covenant on Civil and Political Rights, Article 10 (ibid., § 147); Convention on the Rights of the Child, Article 37(c) (ibid., § 149).
[8] See, e.g., Standard Minimum Rules for the Treatment of Prisoners, Rule 8(d) (ibid., § 156); Standard Minimum Rules for the Administration of Juvenile Justice, Rule 13.4 (ibid., § 158); Rules for the Protection of Juveniles Deprived of their Liberty, Rule 29 (ibid., § 159); Memorandum of Understanding on the Application of International Humanitarian Law between Croatia and the Socialist Federal Republic of Yugoslavia, § 4 (ibid., § 160); Agreement on the Application of International Humanitarian Law between the Parties to the Conflict in Bosnia and Herzegovina, § 2.3 (ibid., § 161); UN Secretary-General’s Bulletin, Section 8(f) (ibid., § 163).
[9] See, e.g., the military manuals of Argentina (ibid., § 165), Canada (ibid., § 168) and Germany (ibid., § 169).
[10] See, e.g., the legislation of Nicaragua (ibid., § 175), Pakistan (ibid., § 177), Philippines (ibid., § 178) and Rwanda (ibid., § 179) and the practice of Malaysia (ibid., § 182).
[11] Peru, Statement before the UN Committee on the Rights of the Child (ibid., § 183); Philippines, Initial Report to the UN Committee on the Rights of the Child (ibid., § 184).
[12] Additional Protocol I, Article 77(4) (adopted by consensus) (ibid., § 148); UN Secretary-General’s Bulletin, Section 8(f) (ibid., § 163); Rules for the Protection of Juveniles Deprived of their Liberty, Rule 29 (ibid., § 159).
[13] Convention on the Rights of the Child, Article 37(c) (ibid., § 149).
[14] Australia, Reservation made upon ratification of the Convention on the Rights of the Child (ibid., § 150).
[15] Canada, Reservation made upon ratification of the Convention on the Rights of the Child (ibid., § 151); New Zealand, Reservations and declarations made upon ratification of the Convention on the Rights of the Child (ibid., § 154); United Kingdom, Reservations and declarations made upon ratification of the Convention on the Rights of the Child (ibid., § 155).
[16] Additional Protocol I, Article 77(2) (adopted by consensus) (cited in Vol. II, Ch. 39, § 379).
[17] Convention on the Rights of the Child, Article 1.
[18] Rwanda, Prison Order (cited in Vol. II, Ch. 37, § 179); Pakistan, Prisons Act (ibid., § 177).