An Austrian national by birth transferred his residence to Germany and naturalised as a German national. The naturalisation in Germany had the effect, in accordance with Austrian law, of causing him to lose his Austrian nationality. The German authorities later withdrew the naturalisation with retroactive effect, on the grounds that the applicant had not disclosed that he was the subject of a criminal investigation in Austria on account of suspected serious fraud, and that he had thus obtained German nationality by deception. The Court held that it is not contrary to EU law for a Member State to withdraw nationality obtained by deception, even if it results in losing EU citizenship, so long as the decision observes the principle of proportionality. Observance of the principle of proportionality requires the person concerned to be afforded a reasonable period of time in order to try to recover the nationality of their Member State of origin.
The case concerns an applicant who was a Ukrainian citizen and a resident of Crimean Peninsular at the time of Crimean annexation to Russia. He was originally issued with a Russian passport in 2014, which was subsequently confiscated as a government initiated verification procedure established he did not comply with the relevant residency requirements to be considered a Russian citizen. The Court, on appeal, sided with the applicant, confirming his right to Russian citizenship despite not complying with all the formal requirements.
In its reasoning the Court relied heavily on the importance to take all the relevant and factual evidence when establishing the legal fact of residence, and basing it on a broad range of evidence about the person's personal and professional life, as well as intentions, not the merely the strict formalistic rules of residence registration, especially in light of consequences of denial of access to citizenship for the applicant, and the circumstances of state succession. The Court refers extensively to international legal instruments, even those Russia hasn't ratified, such as the European Convention on Nationality and its anti-statelessness safeguards, the CoE Convention on the Avoidance of Statelessness in Relation to State Succession, as well as art. 15 UDHR, and other international legal instruments.