A/HRC/37/50 detained arbitrarily, and to have individual rights and duties determined in a due process proceeding.20 16. In addressing the consequences of torture and ill-treatment, States must ensure that survivors obtain redress and have an enforceable right to fair and adequate compensation, including the means for as full rehabilitation as possible.21 Wherever States receive allegations or otherwise have reasonable ground to believe that an act of torture or illtreatment has been committed within their jurisdiction, they have a duty to investigate, prosecute, and punish the perpetrators.22 In case of "serious" (i.e. "gross or systematic") breaches of the peremptory prohibition of torture in one State, all other States are not only entitled, but also legally obliged: (a) to cooperate to bring such abuse to an end through any lawful means at their disposal, (b) not to recognize as lawful any situation created by such violations, and (c) not to aid or assist in maintaining any such situation.23 Depending on the context, the perpetration or participation in acts of torture and ill-treatment may also amount to a war crime or a crime against humanity and, as such, would be subject to universal jurisdiction and exempted from any statute of limitations. C. Migration-related Detention 17. In many parts of the world, States increasingly resort to the criminalization of irregular migration, and to deprivation of liberty as a routine or even mandatory response.24 States detain migrants in both criminal and administrative detention regimes which aim to criminalize and punish breaches of immigration laws or, respectively, to carry out administrative procedures related to arrival, asylum, overstay, residence or return. 1. Deprivation of liberty 18. In generic terms, "deprivation of liberty" or "detention" includes any placement of persons in public or private custodial settings which they are not permitted to leave at will.25 In practice, this may include, for example, prisons or purpose-built detention facilities, closed reception or holding centers, shelters, guesthouses, camps, but also temporary facilities, vessels and private residences. Regardless of the name given to a particular placement or accommodation and its categorization in national law, the decisive question for its qualification as "deprivation of liberty" is whether or not migrants are free to leave.26 In practice, the possibility to leave must not be a merely theoretical option to be exercised at some point in the future, but must be practicable and available at any time. For example, holding migrants at an international border, an offshore facility or an airport transit zone and refusing their immigration while granting them the theoretical right to leave to any other country or territory of their choice still amounts to deprivation of liberty for such time as they are being held, and entitles all affected migrants to the full protection afforded to persons deprived of their liberty under international law.27 2. Treatment and conditions of detention 19. Although any detention of migrants must "take place in appropriate, sanitary, nonpunitive facilities and should not take place in prisons",28 in reality the practice is often the opposite. Numerous press and stakeholder reports have described the appalling physical and hygiene conditions under which migrants are being detained in all regions of the world, 20 21 22 23 24 25 26 27 28 6 Arts.8-10; 13(2); 14(1) UDHR; Arts.9; 12(2); 13; 14 ICCPR. Art.14 CAT. Arts.4-9; 12-13 UNCAT. ILC, Art.40(2), 41(1) and (2) ASR; World_Summit_Outcome, A/RES/60/1, 24.10.2005, §§138-139. A/HRC/17/33, §§12, 19. UNHCR Report, “Beyond_Detention”, 2016. See also the treaty definition in Art.4 OPCAT. UNHCR, Guidelines_on_the_Applicable_Criteria_and_Standards_relating_to_the_Detention _of_Asylum-Seekers_and_Alternatives_to_Detention_(2012), §5-7. ECtHR, Amuur_v._France_(No.19776/92), Jgmt_25.06.1996, §§48-49. CCPR, GC_No.35(2014), §18.