Following the ECtHR’s Kanagaratnam, and Muskhadzhiyeva judgments, the Secretary of State decided that from 1 October 2009 onwards families with children that are arriving at the border and that are not removable within 48 hours after arrival should be accommodated in a family unit.
However, in August 2018, Belgium opened detention facilities for families with children. Article 74/9(3)(4) of the Aliens Act allows for a limited detention of the families with children in case they do not respect the conditions they accepted in a mutual agreement with the Immigration Office to stay in their own house, and/or absconded from the return homes. The closed centre for families is located next to the 127bis repatriation centre near the Brussels National Airport. The Royal Decree of 22 July 2018 (amending the Royal Decree of 2 August 2002) establishes the rules for the functioning of the closed family units near Brussels International airport.  While the Council of State first suspended the Royal Decree in April 2019, it later only annulled some provisions of the aforementioned Royal Decree, maintaining the possibility of detaining families with children for a maximum of 4 weeks. A procedure before the European Court of Human Rights has subsequently been initiated to obtain the annulment.
The current government has agreed that it can no longer detain families with children in closed centres, as a matter of principle. New, alternative measures will be developed to avoid that this measure would be abused to make return impossible.
The detention of unaccompanied children is explicitly prohibited by law. Since the entry into force of the Reception Act, unaccompanied children are in principle no longer placed in detention centres. When they arrive at the border, they are assigned to a so-called Observation and Orientation Centre (OOC) for unaccompanied children. This only applies to those unaccompanied children with regard to whom no doubts were raised about the fact that they are below 18 years of age and are identified as such by the Guardianship Service (see Asylum Procedure: Identification). Also, this OOC is legally considered to be a detention centre at the border, which means that the unaccompanied child is not considered to have formally entered the territory yet. Within 15 calendar days, the Immigration Office has to find a durable solution for the child, which may include return after an asylum application has been refused. Otherwise access to the territory has to be formally granted.
Unaccompanied minors who are caught on the territory without residence permit are sometimes held in detention for the duration of their age assessment procedure. This can sometimes take more than a week before this is rectified. In 2019, 3 children whose age was tested during detention were considered 15 years old after the test and had thus wrongly been held in detention. In 2020, two minor boys were held in detention because of doubts about their declared age. Because the Belgian authorities did not want to carry out a bone test while the boys were in confinement for sanitary reasons (COVID-19), it eventually took 22 days before they were officially declared minors and released from detention. This practice has in the meantime been adapted and in 2021, most minors have been released in 6 days after their arrival.
No other vulnerable categories of asylum seekers are excluded from detention by law. Besides the consideration of the minority of age, no other vulnerability assessment is made whatsoever before deciding on the detention of asylum seekers, especially at the border. In practice, the detention of vulnerable persons remains problematic.
 ECtHR, Kanagaratnam and Others v Belgium, Application No 15297/09, Judgment of 13 December 2011. The Court found a violation of Articles 3 and 5(1) ECHR due to the detention of a Sri Lankan asylum seeking (who was eventually recognised as a refugee) mother with three underage children for more than three months.
 ECtHR, Muskhadzhiyeva and Others v Belgium, Application No 41442/07, Judgment of 19 January 2010. The Court found a violation Articles 3 and 5(1) ECHR due to the administrative detention for one month of a Chechen woman and her four small children who had applied for asylum in Belgium while waiting to be expelled to Poland, the country through which they had travelled to Belgium.
 Arrêté royal du 22 juillet 2018 | Koninklijk besluit van 22 juli 2018.
 Council of State, Decision No 244.190, 4 April 2019.
 Council of State, Decision No 251051 of 24th of June 2021
 Vluchtelingenwerk Vlaanderen acts as one of the applicants in this procedure.
 Article 74/19 Aliens Act.
 Article 40 Reception Act.
 On the technicality of this legal fiction, see inter alia Council of State, Decisions No 102.722, 21 January 2002 and No 57831, 25 January 1996.
 Figures confirmed by the Immigration Office in January 2020.