What remedies are available in the last instance?

Law on Elections to the Seimas (as of2012, in English)

Source: http://www3.lrs.lt/pls/inter3/dokpaieska.showdoc_l?p_id=430477

Article95.5. If the Constitutional Court makes a conclusion that the Law on Elections tothe Seimas has been severely violated or election documents have been falsifiedand this has had an essential influence on the establishment of the electionresults, the Seimas of the Republic of Lithuania may pass one of the followingresolutions: 1) to declare the elections in a single-member constituency or multi-memberconstituency invalid - when, from the vote counting records, it is impossibleto establish essential election results; or

2) to establish real essentialelection results according to the vote counting records or other electiondocuments submitted by electoral committees.