My father naturalized in the United states. However, he never sent in a formal renounciation of citizenship to his former country. After becoming a u.s. citizen he owned property in his former country under his former citizenship. The state department has been made aware of this and I am wondering if they can take away his u.s. citizenship. The country in question allows dual citizenship but my father never got the card and the dual citizen ship came after he acquired his property. Can the state department say that because he never formally renounced his citizenship and maintained his former citizenship after naturalizing his u.s. citizenship is void.