A lawyer can file the claim.
Someone has to find the record first.

The real bottleneck

The hard part is not the law. It is the missing record.

People brace themselves for bureaucracy, and the bureaucracy is real, but it is learnable. The forms have a shape. A good lawyer knows the route through the ministry and has walked it before. That is not where the years go.

Where a claim sits and sits is the evidence: the proof that your great-grandparent was who you say they were, and held the citizenship you are claiming through. That proof is a document issued by an office that has since been renamed, moved across a new border, or burned. It is not in a law office and not in a government portal. It is in an archive abroad, catalogued under an administrative name the family never used, waiting to be requested by someone who can read the hand it was written in.

So the claim stalls not because the law is hard but because the paper is missing. Everything downstream (the apostille, the sworn translation, the filing) assumes a record already in hand. Most people start spending before they know whether it survived.

What has to be on the table

An unbroken chain, and proof the citizenship was real

Underneath their different rules, the routes ask the same two things. First, an unbroken chain of vital records: a birth, a marriage, a death for each generation between you and the qualifying ancestor, each one naming the next. A single missing link and the line is only a story you cannot prove. Second, evidence that the ancestor genuinely held the citizenship. Not that they lived somewhere, but that the state counted them as its own.

Poland. The process is called a confirmation, not a grant: if you qualify, the position is that you were a citizen all along. The state wants the chain of records plus something showing the ancestor was a Polish citizen who never lost that status: a pre-war record giving a Polish place of residence, an interwar passport or military paper, an old voter roll, a consular registration. The vital records do the lineage; these do the citizenship.

Lithuania. Citizenship is restored to the descendants of those who held it before the occupation of 1940 and who left before independence was recovered in 1990, with no limit on the number of generations, so long as the chain holds and both the ancestor's citizenship and its loss can be documented.

Other routes run on the same logic: a documented line of descent back to a qualifying ancestor, and proof of what that ancestor was on paper. The thresholds differ from country to country and they change; the foundation does not. Before any of it, the records have to exist and be found.

The part that surprises people

The border moved. The citizenship did not.

Between the wars, several of these states covered land that today sits inside other countries. A person born a citizen in that period was a citizen regardless of which flag now flies over the village. The claim travels with the citizenship that existed then, not the map as it is drawn now.

For families whose roots lie in those shifted borderlands, this is the whole point. What decides the case is not where the place appears in an atlas today, but what the ancestor was recorded as in, say, 1925: the residence in a pre-war register, the entry in a parish book kept while the old administration was still in place. The village may answer to a different country and a different language now. The record does not care.