For asylum and return (i.e. expulsion) procedures to be implemented effectively, people need to be at the disposal of the authorities so that any measure requiring their presence can be taken without delay. To achieve this, EU Member States may decide to hold people in closed facilities. Less intrusive measures, which are usually referred to as alternatives to detention, reduce the risk that deprivation of liberty is resorted to excessively.

The paper is available on the FRA website here