One of his ancestors was Jacob ben Jehiel Loans, personal physician to emperor Frederick III, ennobled for his medical achievements, and also Hebrew teacher of the well-known humanist, lawyer and philosopher Johannes Reuchlin.
In 1470, three of his father's brothers, including Rabbi Elias, were prosecuted in Endingen, brought before the emperor on charges that eight years earlier they had performed a ritual murder at Sukkot.
In 1476, along with the entire Jewish community of that town, the family fled (pursued by Swiss mercenaries) to Haguenau, where Josel was born, possibly as early as that same year.
While still young, he worked for the welfare of his coreligionists, and, reportedly, was instrumental in thwarting the hostile plans of Johannes Pfefferkorn,[1] a converted Jew who turned a rabid antisemite.
As such he had "to keep his eyes open in special care of the community," and possessed the right to issue enactments for the Jews of his district and to put under the ban (cherem, the equivalent of excommunication) refractory members.
[1] Becoming steadily better known, even beyond the borders of Alsace, as a defender of Jewish communities in religious and legal matters, Josel gradually acquired a status as an advocate, and even leader ("Befehlshaber") of all the Jews in the German empire also having the title of Imperial governor.
Soon after Charles V ascended the throne at Aachen in 1520, Josel procured a charter or letter of protection from him for the whole German Jewry, confirmed ten years later in the Edict of Innsbruck, May 18, 1530.
In 1530, in the presence of the emperor and his court at Augsburg, Josel had a public disputation with the baptized Jew Antonius Margaritha, who had published a pamphlet Der gantze Jüdisch Glaub (The Whole Jewish Belief) full of libelous accusations against Judaism.
While still occupied with the Augsburg articles, Josel had to hurry to the court of Charles V of Brabant and Flanders in order to defend the calumniated German Jews there (1531).
At the Reichstag of Regensburg (1532) he tried in vain to dissuade the proselyte Solomon Molko from carrying out his fantastic plan to arm the German Jews and to offer them as a help to the emperor in his wars with the Turks.
[1] In 1535, Josel traveled to Brandenburg-Ansbach to intercede with the margrave Georg in favor of the Jews of Jägerndorf, who had been falsely accused and thrown into prison; and he obtained their freedom.
But at a meeting in Frankfurt (1539) he found occasion to speak to the prince, whose attention he attracted by refuting, in a public dispute with the reformer Bucer, some spiteful assertions about the Jews.
In the same Reichstag Philipp Melanchthon proved the innocence of the thirty-eight Jews who had been burned in Berlin in 1510, and this helped to induce Kurfürst Joachim of Brandenburg to grant Josel's request.
"[3] Michael writes that Josel asked the city of Strasbourg to forbid the sale of Luther's anti-Jewish works; they refused initially, but relented when a Lutheran pastor in Hochfelden argued in a sermon that his parishioners should murder Jews.
In the Speyer letter of protection, referred to above, the emperor disapproved of the accusation of ritual murder, and he ordained that no Jew should be put in prison or sentenced for this crime without sufficient proof.
The letter requested that the Council assist Josel in advocating on behalf of the Jews in Saxony and Hesse, and to stop printing Luther's antisemitic tracts.
Through Granvella, the influential counselor of the emperor, Josel obtained an imperial order to the army and a mandate to the Christian population in favor of the Jews, so that they were not molested in the course of the war.