The Court held that it is not contrary to EU law for Member States to withdraw citizenship obtained by deception, even if the effect is to also withdraw citizenship of the Union, so long as the decision observes the principle of proportionality.
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.