While each state determines under its own law who are its nationals, the nationality requirement sometimes causes undue problems. For instance, states may withhold citizenship from persons who have been settled in their territories for generations. In some post-soviet states, such as Estonia and Latvia, a considerable number of persons, most of Russian background, have not automatically acquired citizenship and, as a result, are not allowed to vote and stand for elections. Although major efforts have been made to naturalise those persons in the meantime, in both countries more than a few residents with undetermined citizenship are still disenfranchised in national elections.