August 1912, a legal case breaks out in Livorno within the Jewish community, involving central historiographical themes of the modern and contemporary age. The Israelitic University of Livorno and the Major Rabbi Samuele Colombo were sued by the legal memory written by a lawyer that was defending a young Jewish woman, who saw her marriage to a co-religionist annulled by the rabbinical authorities. One of the bride's ancestors, who lived in Livorno a century before the facts, had been declared a "mamzèr", i.e. born of an illicit union. The law (Deuteronomy 23,3) is clear: the marriage must be annulled. The memory of the young woman's lawyer, Angiolo Cohen, an assimilated Jew, accuses the community of being affected by religious fanaticism. Important issues arose from this legal dispute, such as the principle of the eternity of the Torah, the competition of different legal systems within the unitary state, and the meaning of Jewish orthodoxy in the contemporary world. The case was eventually won by the Israeli Community of Livorno and resonated in Italian and European public opinion. The presentation aims to offer insights on social relations within the Jewish community of Livorno and with the majority society. It will be seen how the case was reported in the newspapers of the time, such as Il telegrafo di Livorno, and was then discussed in the Vessillo Israelitico in the issue of September 1912. Finally, the same case was taken up 50 years later, becoming the starting point for a debate in the pages of La Rassegna Mensile di Israel featuring Dante Lattes and Yoseph Colombo, showing how central the city of Livorno was to Italian Jewish life in the early 20th century, representing a privileged viewpoint for the study of the social and cultural dynamics of Jewish society in the transition to contemporaneity.