When detention has been ordered by administrative authorities, Member States shall: (a) either provide for a speedy judicial review of the lawfulness of detention to be decided on as speedily as possible from the beginning of detention; (b) or grant the third-country national concerned the right to take proceedings by means of which the lawfulness of detention shall be subject to a speedy judicial review to be decided on as speedily as possible after the launch of the relevant proceedings. In such a case Member States shall immediately inform the third-country national concerned about the possibility of taking such proceedings. The third-country national concerned shall be released immediately if the detention is not lawful. 3. In every case, detention shall be reviewed at reasonable intervals of time either on application by the third-country national concerned or ex officio. In the case of prolonged detention periods, reviews shall be subject to the supervision of a judicial authority. 4. When it appears that a reasonable prospect of removal no longer exists for legal or other considerations or the conditions laid down in paragraph 1 no longer exist, detention ceases to be justified and the person concerned shall be released immediately. 5. Detention shall be maintained for as long a period as the conditions laid down in paragraph 1 are fulfilled and it is necessary to ensure successful removal. Each Member State shall set a limited period of detention, which may not exceed six months. 6. Member States may not extend the period referred to in paragraph 5 except for a limited period not exceeding a further 12 months in accordance with national law in cases where regardless of all their reasonable efforts the removal operation is likely to last longer owing to: (a) a lack of cooperation by the third-country national concerned, or (b) delays in obtaining the necessary documentation from third countries.’ 5 Under Article 20 of Directive 2008/115, Member States are required to bring into force the laws, regulations and administrative provisions necessary to comply with the directive, with the exception of Article 13(4), by 24 December 2010. 6 In accordance with Article 22 of the directive, it entered into force on 13 January 2009. National legislation 7 Directive 2008/115 was transposed into Bulgarian law by the Law on foreign nationals in the Republic of Bulgaria (DV No 153 of 1998), as amended on 15 May 2009 (DV No 36 of 2009) (‘the Law on foreign nationals’). 8 According to the referring court, Article 15(4) of the directive has, however, not yet been transposed into Bulgarian law.