RAMADAN v. MALTA JUDGMENT 11 These rights shall be exercised in accordance with the conditions and limits defined by the Treaties and by the measures adopted thereunder.” (a) Rottmann v. Freistaat Bayern, 2 March 2010, CJEU, C-135/08 [2010] ECR II-05089 45. Dr Rottmann was 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 Dr Rottmann 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. Such a decision, however, 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 Dr Rottmann’s statelessness also entailed the loss of EU citizenship. The Court of Justice of the European Union (CJEU) ruled that an EU Member State’s decision to deprive an individual of citizenship, in so far as it implied the loss of the status of EU citizen and the deprivation of the attached rights, fell within the ambit of EU law and, therefore, must be compatible with its principles. 46. 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 EU citizenship, in addition to citizenship of that Member State. Such a decision, however, must 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. (b) Gerardo Ruiz Zambrano v. Office national de l’emploi (ONEm), 8 March 2011, CJEU, C-34/09 [2011] ECR I-01177 47. Mr and Ms Zambrano, of Colombian nationality, were refused refugee status in Belgium but were not sent back to Colombia on account of the civil war in that country. From 2001, Mr and Ms Zambrano were then registered as resident in Belgium and Mr Zambrano worked there for a certain time, even though he did not hold a work permit. In 2003 and 2005, Mr and Ms Zambrano had two children who acquired Belgian nationality in accordance with the Belgian legislation applicable at that time. The competent authorities refused to accede to Mr and Ms Zambrano’s application to regularise their situation and to take up residence as ascendants of Belgian nationals. 48. According to the CJEU, Article 20 of the TFEU precluded national measures which had the effect of depriving citizens of the Union of the genuine enjoyment of the substance of the rights conferred by virtue of their status as citizens of the Union. The CJEU concluded that Article 20 TFEU