A/HRC/30/37 Principle 21 Specific measures for non-nationals, including migrants regardless of their migration status, asylum seekers, refugees and stateless persons 42. Non-nationals, including migrants regardless of their status, asylum seekers, refugees and stateless persons, in any situation of deprivation of liberty shall be informed of the reasons for their detention and their rights in connection with the detention order. This includes the right to bring proceedings before a court to challenge the arbitrariness and lawfulness and the necessity and proportionality of their detention, and to receive without delay appropriate and accessible remedies. It also includes the right of the above-mentioned persons to legal assistance in accordance with the basic requirement of prompt and effective provision of legal assistance, in a language that they use and in a means, mode or format they understand, and the right to the free assistance of an interpreter if they cannot understand or speak the language used in court. 43. Irrespective of the body responsible for their detention order, administrative or other, such non-nationals shall be guaranteed access to a court of law empowered to order immediate release or able to vary the conditions of release. They shall promptly be brought before a judicial authority before which they should have access to automatic, regular periodic reviews of their detention to ensure that it remains necessary, proportional, lawful and non-arbitrary. This does not exclude their right to bring proceedings before a court to challenge the lawfulness or arbitrariness of their detention. 44. Proceedings of challenges to decisions regarding immigration detention must be suspensive to avoid expulsion prior to the case-by-case examination of migrants in administrative detention, regardless of their status. 45. The deprivation of liberty as a penalty or punitive sanction in the area of immigration control is prohibited. 46. The deprivation of liberty of an unaccompanied or separated migrant or of an asylum-seeking, refugee or stateless child is prohibited. Detaining children because of their parents’ migration status will always violate the principle of the best interests of the child and constitutes a violation of the rights of the child. II. Guidelines Guideline 1 Scope of application 47. The right to bring proceedings before a court to challenge the arbitrariness and lawfulness of detention and to receive without delay appropriate and accessible remedies is applicable: (a) To all situations of deprivation of liberty, including not only to detention for purposes of criminal proceedings but also to situations of detention under administrative and other fields of law, including military detention, security detention, detention under counter-terrorism measures, involuntary confinement in medical or psychiatric facilities, migration detention, detention for extradition, arbitrary arrests, house arrest, solitary confinement, detention for vagrancy or drug addiction, and detention of children for educational purposes; (b) Irrespective of the place of detention or the legal terminology used in the legislation. Any form of deprivation of liberty on any ground must be subject to effective oversight and control by the judiciary. 12