HASSAN v. THE UNITED KINGDOM JUDGMENT – SEPARATE OPINION 63 understood to cover only subsequent practice common to all Parties, as well as requiring that the practice be concordant, common and consistent. Subsequent practice of States Parties which does no fulfil these criteria may only constitute a supplementary means of interpretation of a treaty (see Report of the International Law Commission on the Work of the Eighteenth Session (Geneva, 4 May to 19 July 1966), 1966 (2) Yearbook of the International Law Commission 173, p. 222). Bearing this in mind, it may be questioned whether the State practice referred to by the majority in the present case can be considered to fulfil, in substance, the criteria underlying the subsequent practice rule of Article 31 § 3 (b) of the Vienna Convention as developed in international law. Furthermore, and most importantly in my view, in assessing whether a State practice fulfils the criteria flowing from Article 31 § 3 (b), and thus plausibly modifies the text of the Convention (see paragraph 101 of the judgment), there is, on the one hand, a fundamental difference between a State practice clearly manifesting a concordant, common and consistent will of the Member States to collectively modify the fundamental rights enshrined in the Convention, towards a more expansive or generous understanding of their scope than originally envisaged, and, on the other, a State practice that limits or restricts those rights, as in the present case, in direct contravention of an exhaustive and narrowly tailored limitation clause of the Convention protecting a fundamental right. 14. Thirdly, the Court draws further support for its reliance on State practice, in not derogating under Article 15 in respect of detentions under the Third and Fourth Geneva Conventions during international armed conflict, on the practice of States to refrain from derogating under Article 4 of the International Covenant on Civil and Political Rights (ICCPR) with regard to such activities. Such reliance is however clearly inapposite in my view, as there is a fundamental distinction to be made between the wording and scope of Article 5 § 1 of the Convention, on the one hand, and Article 9 of the ICCPR and of Article 9 of the Universal Declaration on Human Rights, on the other. The former is exhaustive, as regards permissible grounds of detention, whereas the latter is not, as they are limited to a general prohibition against arbitrary forms of detention. Baroness Hale of Richmond expressed this viewpoint in very clear and eloquent terms in her speech in the House of Lords’ judgment in the Al-Jedda case (cited at paragraph 39 of the Court’s judgment), where she stated (§ 122): “ ... There is no doubt that prolonged detention in the hands of the military is not permitted by the laws of the United Kingdom. Nor could it be permitted without derogation from our obligations under the European Convention on Human Rights. Article 5(1) of the Convention provides that deprivation of liberty is only lawful in defined circumstances which do not include these. The drafters of the Convention had a choice between a general prohibition of “arbitrary” detention, as provided in Article 9 of the Universal Declaration of Human Rights, and a list of permitted grounds for detention. They deliberately chose the latter. They were well aware of