12 K2 v. THE UNITED KINGDOM DECISION the necessary procedural safeguards, including whether the person deprived of citizenship was allowed the opportunity to challenge the decision before courts affording the relevant guarantees; and whether the authorities acted diligently and swiftly (see Ramadan v. Malta, cited above, §§ 86-89). In view of the relevance of procedural safeguards to the assessment of arbitrariness, the Court considers that in the present case it would be artificial to separate the applicant’s substantive and procedural complaints. It will therefore address these complaints together. 51. Although the applicant does not appear to have invoked the guarantees under the procedural limb of Article 8 either in the judicial review proceedings or before SIAC, in view of the fact that the procedural and substantive complaints are not easily separated, and in light of its findings at paragraphs 52-67 below, the Court does not need to reach any firm conclusion on whether the applicant has exhausted domestic remedies in respect of his procedural complaint within the meaning of Article 35 § 1 of the Convention. (a) Arbitrariness i. Was the deprivation in accordance with the law? 52. It is not suggested that the decision to deprive the applicant of his citizenship was anything other than “in accordance with the law”. Pursuant to section 40(2) of the 1981 Act the Secretary of State has a power to make an order depriving a person of his British citizenship on the ground that the deprivation is “conducive to the public good” (see paragraph 36 above). In addition, the Crown enjoys a common law prerogative power to exclude a person from the United Kingdom. Although in the judicial review proceedings the applicant argued that the statutory scheme impliedly precluded the exercise of the prerogative power to exclude an individual on conducive grounds while an appeal against deprivation of citizenship was pending (see paragraphs 9 and 15 above), both the High Court and the Court of Appeal found that the relevant legislation could not be so construed (see paragraphs 12 and 15 above). The applicant does not repeat that complaint before this Court and, in any event, the Court has repeatedly stated that the interpretation of domestic legislation is primarily a matter for the national courts (see, among many examples, Söderman v. Sweden [GC], no. 5786/08, § 102, ECHR 2013 and Nejdet Şahin and Perihan Şahin v. Turkey [GC], no. 13279/05, § 49, 20 October 2011). Furthermore, the applicant did not contest the foreseeability or quality of the law either before the domestic courts or before this Court. ii. Did the authorities act diligently and swiftly? 53. Furthermore, there is no evidence of any failure on the part of the Secretary of State to act diligently and swiftly in deciding to deprive the