A/HRC/7/4 page 23 arrest. Some have been held incommunicado at undisclosed places of detention, where they are at risk of ill-treatment. The Working Group was further informed of cases in which military laws had been amended by executive decree during a state of emergency in order to give power to military courts to try civilians for a wide range of offences and in some cases with retroactive effect. 2. Concerns 64. The Working Group reiterates its concerns and recalls that it has continuously considered that states of emergency are a root cause of arbitrary detentions and cautioned against their promulgation. Given the frequency of arbitrary detentions occurring in such situations, it would like to remind Governments that they may only be imposed in strict compliance with the principle of proportionality. Each measure taken thereunder, including the suspension of and restrictions on derogable fundamental rights and freedoms, must also pursue a legitimate goal, be necessary and appropriate to the goal to be achieved.20 Whatever the threat, under no circumstances may detention based on emergency legislation last indefinitely. The Working Group attaches particular importance to the existence of effective internal control mechanisms over the legality of detention. It considers the remedy of habeas corpus as one of the most effective means of preventing and combating arbitrary detention. It must not be suspended or rendered impracticable in states of emergency. 65. Broadening military jurisdiction in order to try civilians with retroactive effect during states of emergency inevitably touches upon the right to fair trial guarantees entrenched in article 14 of the International Covenant on Civil and Political Rights (ICCPR) and article 10 of the Universal Declaration of Human Rights. In the light of its experience, the Working Group has always taken a cautious approach regarding military or special jurisdictions in general and extending such jurisdiction to civilians in particular. It has done so since, in almost all cases, military courts involve serious risks of arbitrariness, because of the applicable procedure and the corporative nature of their membership. They all too often give the impression of applying a double standard, depending on whether the person on trial is a civilian or a member of the military. 66. The Working Group understands that article 14 of the ICCPR does not rule out trials before military courts as long as all fair trial standards set out in article 14 are guaranteed. However, it is of the opinion that States must provide objective and serious justification for trying civilians before military courts. Such trials may only be conducted if civilian courts are unable to deal with a specific class of individuals or offences. Trials of civilians before military or special courts must be the exception.21 20 Human Rights Committee general comment No. 29 (2001) on derogations during a state of emergency, in particular paragraphs 4 and 5. 21 Human Rights Committee general comment No. 32 (2007) on article 14: Right to equality before courts and tribunals and to a fair trial, paragraph 22.