A/HRC/13/30 60. The detention of minors, particularly of unaccompanied minors, requires even further justification. Given the availability of alternatives to detention, it is difficult to conceive of a situation in which the detention of an unaccompanied minor would comply with the requirements stipulated in article 37 (b), clause 2, of the Convention on the Rights of the Child, according to which detention can be used only as a measure of last resort. 61. Further guarantees include the fact that a maximum period of detention must be established by law and that upon expiry of this period the detainee must be automatically released. Detention must be ordered or approved by a judge and there should be automatic, regular and judicial, not only administrative, review of detention in each individual case. Review should extend to the lawfulness of detention and not merely to its reasonableness or other lower standards of review. The procedural guarantee of article 9 (4) of the International Covenant on Civil and Political Rights requires that migrant detainees enjoy the right to challenge the legality of their detention before a court. Established time limits for judicial review must be obtained in “emergency situations” when an exceptionally large number of undocumented immigrants enter the territory of a State. All detainees must be informed as to the reasons for their detention and their rights, including the right to challenge its legality, in a language they understand and must have access to lawyers. 62. These human rights and principles are not always guaranteed. The Working Group has visited countries on official mission where detention of migrants in an irregular situation is mandatory and automatic, without a necessity criteria being applied. It has observed that some national laws do not provide for detention to be ordered by a judge, or for judicial review of the detention order. Detainees often do not enjoy the right to challenge the legality of their detention. There is no maximum length of detention established by law, which leads to prolonged or, in the worst case, potentially indefinite detention in cases, for example, where the expulsion of a migrant cannot be carried out for legal or practical reasons. 63. This is a serious concern, as there are situations in which a removal order cannot be executed because, for example, the consular representation of the country of origin of the migrant does not cooperate or there is simply no means of transportation available to the home country. An example of a legal limitation for removal is the principle of nonrefoulement. In such cases, where the obstacle to the removal of the detained migrants does not lie within their sphere of responsibility, the detainee should be released to avoid potentially indefinite detention from occurring, which would be arbitrary. 64. The principle of proportionality requires that detention always has a legitimate aim, which would not exist if there were no longer a real and tangible prospect of removal. The Human Rights Committee has reasoned along very similar lines beginning with the case of A. v. Australia.30 Opinion No. 45/200631 of the Working Group could serve as a reference for further details on the applicable legal concepts. 65. During country missions, the Working Group has sometimes witnessed unacceptable substandard conditions of detention in overcrowded facilities that affect the health, including the mental health, of irregular migrants, asylum-seekers and refugees, and increase the risk of a whole range of further violations of human rights, i.e. of economic, social and cultural rights. Alternatives to detention can take various forms: reporting at regular intervals to the authorities; release on bail; or stay in open centres or at a designated place. Such measures are already successfully applied in a number of countries. They must however not become alternatives to release. 30 31 18 Communication No. 560/1993, A. v. Australia, Views adopted on 3 April 1997, para. 9.4. A/HRC/7/4/Add.1, p. 40. GE.10-10294