European legal and policy framework on immigration detention of children Belgium’s permanent Complaint Commission dealing with individual complaints has declared only 60.6 % of lodged complaints admissible, and only nine of them well founded, Myria reports.425 Most EU Member States have set up National Preventive Mechanisms under OPCAT, often represented by Ombudsmen (Section 7.3). A number of them can also review individual complaints. Complaint mechanisms are ineffective if people do not know of them. For example, in Greece, children are not made aware of their right to make a complaint to the Greek Ombudsman.426 Therefore, it is important to ensure that children become aware of the available complaint mechanisms in a way suitable to their age, maturity and language skills. Providing information in a child-friendly way is a precondition to ensure children know their rights. This can be done, for instance, by informing them of their right to make a complaint upon their arrival at the detention centre, as happens in Latvia and Sweden.427 In many cases, NGOs who work in detention facilities, providing social or legal counselling, may provide information on how to lodge a complaint. Another way to help people make complaints is by providing complaint boxes in accessible places within the facility. FRA observed this in the hotspot in Leros (Greece), for example. However, together with the boxes there must be a transparent procedure to follow up complaints systematically. 94 languages.428 Similarly, in the United Kingdom, a childfriendly complaint form is available in 14 languages.429 For unaccompanied children, some EU Member States, for example Latvia or Slovenia, require that the complaint be formally lodged by the guardian.430 Where the guardian does not regularly visit the child or there is no regular contact, this can constitute an additional practical barrier. Conclusion National Human Rights Institutions, particularly National Preventive Mechanisms that EU Member States set up under the OPCAT, are important in preventing unlawful or arbitrary detention. They complement the work done by international monitoring bodies, principally the CPT. National child protection authorities could play an important role in safeguarding the best interests of the child and in promoting the well-being of detained children. Child protection authorities could be involved in assessing the best interests of the child, in the oversight of child detention standards and in the smooth running of complaint mechanisms. Nevertheless, in many Member States child protection authorities are not actively involved in the process of child detention. One obstacle to providing information is language. This can be overcome by supplying information in a language that the child or their guardian understands. For example, Poland makes information regarding the complaints mechanism available in 16 foreign The Schengen evaluation mechanism regularly reviews the correct application of the EU  return acquis by EU Member States. It assesses compliance with standards explicitly included in Articles 10 and 15 to 17 of the Return Directive, which also includes the treatment of children in return procedures and assessing the best interests of the child, in the context of pre-removal detention. 425 Le Centre interfédéral pour l’égalité des chances et la Lutte contre le Racisme, Myria, Le Service de lutte contre la pauvreté, la précarité et l’exclusion sociale, Kinderrechtencommissariaat, Le Délégué général aux droits de l’enfant de la Fédération Wallonie Bruxelles, Le Médiateur fédéral, La Commission de la protection de la vie privée, Ombudsmann der Deutschsprachigen Gemeinschaft, le Médiateur de la Wallonie et de la Fédération Wallonie, Comité permanent de contrôle des services de renseignement et de sécurité, Conseil supérieur de la Justice, Institut pour l’égalité des femmes et des hommes (2015), Examen Périodique Universel de la Belgique auprès du Conseil des Droits de l’Homme des Nations Unies Second cycle – 24e Session en Janvier 2016 Compilation de contributions, Brussels, pp. 64-65. 426 Greece, UNHCR Detention Office. 427 Latvia, State Border Guard (Valsts robežsardze), Latvian Centre for Human Rights (Latvijas Cilvēktiesību centrs), 14 March 2016, Letter No. 23.1–1/739; Sweden, Swedish Migration Agency (Migrationsverket), 9 February 2016. 428 Poland, Headquarters of Border Guard (Komenda Główna Straży Granicznej), reply to Helsinki Foundation for Human Rights to the request for disclosure of public records, 17 February 2016, KG-OI-III.0180.8.2016.KT. 429 United Kingdom, Her Majesty’s Inspectorate of Prisons (2014) Report on an unannounced inspection of Cedars pre-departure accommodation and overseas family escort, para. 2.19. 430 Latvia, State Border Guard (Valsts robežsardze), Latvian Centre for Human Rights (Latvijas Cilvēktiesību centrs), 14 March 2016, Letter No. 23.1–1/739. Slovenia, Ministry of Interior.