The acquisition of nationality in Ukraine is based on both ius sanguinis and/or ius soli principles depending on the specific situation and respective backgrounds of the case.
Ukrainian citizenship can be acquired by one of the following procedures: Restoration; Naturalisation; Adoption; Affiliation (very similar to the acquisition of the Ukrainian citizenship by birth, when one of the parents of a child is a foreigner or stateless person and the other parent is Ukrainian); Establishment of guardianship over a person (child or an incapable person) by Ukrainian citizen; or by other grounds foreseen by the international treaties of Ukraine.
The Constitution of Ukraine states that only sole citizenship is permitted in Ukraine. However, Ukrainian citizenship is not automatically lost in the case of acquiring foreign citizenship. The termination process for a Ukrainian citizenship is complex, and there is an absence of a mechanism for the state authorities to become aware of the acquisition of another foreign citizenship by the Ukrainian citizens, as well as an absence of criminal or administrative responsibility for obtaining second citizenship. All of this leads to the numerous cases of dual citizenship.
Under Ukrainian legislation, if a citizen of Ukraine acquires the citizenship of another state, such a person is still only recognized as a citizen of Ukraine in legal relations.
Dual citizenship also legally exists due to the ratification by Ukraine of the European Convention on Nationality, according to which the participants of the treaty are required to recognize multiple citizenships in certain cases. For example, children born to parents from different countries are allowed to keep two citizenships.
However, it should be stressed that while there is no direct and clearly expressed ban of dual citizenship for the Ukrainian citizens, foreigners are demanded to renounce their original citizenship if they desire to obtain citizenship of Ukraine by naturalisation. Such foreigners undertaking to withdraw their original citizenship, can do this during a 2-year period and until such a withdrawal is made, they would not receive passports as citizens of Ukraine, but instead, temporary identity cards as citizens of Ukraine.