10 K2 v. THE UNITED KINGDOM DECISION personally acting, in almost all conceivable instances, under direction from ministers. 43. The defining characteristic of the prerogative is that its exercise does not require the approval of Parliament. However, an instruction made under an order in council (the main form of prerogative legislation) is subject, in principle, to judicial review. C. European Union law 44. In Rottmann v. Freistaat Bayern, 2 March 2010, CJEU, C-135/08 [2010] ECR II-05089, the applicant had been born a citizen of Austria. After being accused in Austria of serious fraud in the exercise of his profession, he moved to Germany where he applied for naturalisation. By acquiring German citizenship he lost his Austrian citizenship by operation of the law. Following information from the Austrian authorities that he was the subject of an arrest warrant in their country, the German authorities sought to annul his acquisition of German citizenship on the grounds that he had obtained it fraudulently. This decision had the effect of rendering him stateless. The referring court wished to know if this was a matter that fell within the scope of EU law, as the applicant’s statelessness also entailed the loss of Union citizenship. The Court of Justice of the European Union (CJEU) ruled that an EU Member State decision to deprive an individual of citizenship, in so far as it implied the loss of status of EU citizen and the deprivation of attached rights, fell within the ambit of EU law and, therefore, had to be compatible with its principles. 45. The CJEU concluded that it was legitimate for a Member State to revoke naturalisation on account of deception, even when the consequence was that the person lost their Union citizenship in addition to citizenship of that Member State. However, such a decision had to comply with the principle of proportionality, which, among other things, required a reasonable period of time to be granted in order for the person to recover the citizenship of his or her Member State of origin. COMPLAINTS 46. The applicant complained under Article 8 of the Convention that the decisions to deprive him of his British citizenship and exclude him from the United Kingdom breached his right to respect for his family and private life and amounted to an attack on his reputation. He further complained that there were inadequate procedural safeguards to ensure effective respect for his Article 8 rights as there was very limited disclosure of the national