A/HRC/30/37 Guideline 2 Prescription in national law 48. A strict legality requirement is applicable to both the form of the legal basis and the procedure for its adoption. The legal framework that establishes the process to challenge the arbitrariness and lawfulness of detention shall have a sufficient degree of precision, be drafted in clear and unambiguous language, be realistically accessible and ensure that the exact meaning of the relevant provisions and the consequences of its application are foreseeable to a degree reasonable for the circumstances. 49. Any restriction on liberty must be authorized in national legislation. Depending on the national legal system, restrictions may be based on the Constitution or in the common law. Legislative acts are to be drafted in accordance with the procedural provisions of the Constitution. Guideline 3 Non-derogability 50. In times of public emergency threatening the life of the nation and the existence of which is officially proclaimed, States may take measures to accommodate practical constraints in the application of some procedural elements of the right to bring proceedings before a court to challenge the arbitrariness and lawfulness of detention and to obtain without delay appropriate and accessible remedies only to the extent strictly required by the exigencies of the situation, provided that: (a) The court’s authority to decide without delay on the arbitrariness and lawfulness of detention, and to order immediate release if the detention is not lawful, is not itself diminished; (b) The duty of relevant authorities to give immediate effect to an ord er for release is not diminished; (c) Such measures are prescribed by law, necessary in the exigencies of the situation (including by virtue of the fact that less restrictive measures would be insufficient to achieve the same purpose), proportionate and no n-discriminatory; (d) Such measures apply temporarily, only for as long as the exigencies of the situation require, and are accompanied by mechanisms to review periodically their continued necessity and proportionality; (e) Such measures are consistent with ensuring fair, effective and adversarial proceedings; (f) Such measures are not otherwise inconsistent with international law. Guideline 4 Characteristics of the court and procedural guidelines for review of the detention 51. The court reviewing the arbitrariness and lawfulness of the detention must be a different body from the one that ordered the detention. 52. The competence, independence and impartiality of such a court should not be undermined by procedures or rules pertaining to the selection and appointment of judges. 53. In undertaking the review of the detention, the court has the authority: (a) To consider the application as a matter of urgency. Adjudication of the case, including time for preparation of the hearing, should take place as expeditiously as possible, and should not be delayed because of insufficiency of 13