This is the most consequential unresolved question in Jewish life, because it decides who can marry whom, who is buried where, and who gets citizenship. The rabbinic rule is matrilineal — a Jew is the child of a Jewish mother, or a convert — and its origin is debated by historians. Reconstructionist Judaism recognised patrilineal descent in 1968 and the American Reform rabbinate in 1983, both requiring that the child be raised with public acts of Jewish identity; British Reform, most European progressive movements, and the Conservative movement did not follow, so the divide is not simply liberal against traditional. Israel's Law of Return grants immigration rights to anyone with one Jewish grandparent, a definition consciously chosen to mirror the Nuremberg Laws so that everyone the Nazis would have killed has somewhere to go. The Chief Rabbinate, which controls marriage, burial and conversion for Jews in Israel, applies the matrilineal rule strictly. The result is several hundred thousand Israeli citizens — mostly from the former Soviet Union — who serve in the army, pay taxes, and cannot marry in their own country, and who fly to Cyprus to do it.