I mmigration detention is an administrative measure and should therefore not be punitive—either in nature or in its impact. It should be authorized only when it is necessary, reasonable and proportionate to the legitimate purpose to be achieved, and only if less coercive alternatives cannot be found. Authorities usually resort to such form of detention for various purposes and at various stages of the immigration process, including upon arrival, during the processing of protection or legal claims (including asylum procedures), and in preparation for departure (including forced removal). Not all of these purposes constitute legitimate grounds for detention, and some may amount to arbitrary detention. Legitimate aims, such as health checks, may sometimes be used in a discriminatory or disproportionate manner against certain groups, including on the basis of gender identity. Some reception centers are characterized by restrictions on movement and partial deprivation of liberty (such as nighttime curfews or prohibitions on movement beyond predefined perimeters), and therefore amount to de facto detention facilities. Other centers, usually encountered upon arrival (e.g. at airports) or purpose-built facilities for migrants whose asylum claims have been rejected, are stricto senso places of detention. So-called off-shore detention facilities or deprivation of liberty on vessels must also be on the radar of torture prevention bodies, as risks of abuse are particularly acute in such settings. LGBTI migrants may also face restriction of movement or even deprivation of liberty in refugee camps (see below, “Deprivation of liberty in grounds related to migration”). Risks of human rights violations, including torture and other forms of ill-treatment, are particularly high across all immigration deten-