Lithuania has chosen to have constitutional review of legal acts by the Constitutional Court of Republic of Lithuania. The Constitutional court can decide inter alia whether legal acts contradict to the provisions of Constitution. Constitutional Court also can provide interpretations of laws. This article analyses whether interpretation of law could be applied retroactively. Particularly the Ruling of Constitutional Court of 13 November 2006 providing interpretation of Law on Citizenship is analyzed in this Article. Authors emphasize that citizenship grants certainty right to persons. One of the rights is a right to restitution of property which was nationalized during soviet times. Only citizens of Lithuania have a right to restitution, therefore who are acknowledged citizens is important to other rights of persons. Article analyzes whether ruling of Constitutional Court narrowing list of persons who can be acknowledged as Lithuanian citizens could be applied retroactively i.e. to the status of persons which they have prior to a ruling of Constitutional Court.