Theodosius was the Roman Augustus of the East, appointed by the Emperor Gratianus in 379 CE. He was baptized a Christian a year later and set out on a campaign to ameliorate the relations of his Christian subjects, primarily through the prohibition of Arianism and pagan cult practices. Judaism also came under the gun, although not with the same level of invective as under previous rulers.
In the Codex Theodosianus are found a number of laws aimed at the marginalization and suppression of the Jewish faith, although three particular laws actually support Jewish interests against those of the Christians. The impetus for these laws was a power struggle between Theodosius and Ambrose, the bishop of Milan. Following the burning of a synagogue at Callinicum, Theodosius ordered it rebuilt, which compelled Ambrose to refuse to have mass performed in his presence. This was a challenge to imperial authority that could not be tolerated. These three laws were enacted over the course of three and a half years to undermine Ambrose’s hegemony within Theodosius’ kingdom. This effectively empowered Jewish leadership, but also hastened their downfall.
The first law was enacted in 390 CE (CT 13.5.18). It dealt with the obligation of Jews and Samaritans to acts as shipmasters over goods being transported. The law exempted the financially destitute. The next law, from 392 CE (CT 16.8.8), gave the Jewish patriarchs the right to judicial autonomy in their communities, particularly the right to banish apostates without fear of forced reinstatement by Roman authorities (legitimate or otherwise). The last law, from 393 CE (CT 16.8.9), directly forbid the destruction of Jewish synagogues. Subsequent rulers would tack stipulations onto these laws to prevent Jewish autonomy from encroaching upon Christianity’s authority; but the laws also galvanized a flourish of Jewish building campaigns, which catalyzed further laws prohibiting new synagogues form being built, and, ultimately, the abolishment of the Jewish patriarchate by Theodosius II in 429 CE.
Peter Shäfer’s statement succinctly describes the political expediencies at the root of these pro-Jewish decrees:
In view of such legislation, it is hardly appropriate to regard the “great assault on the Jews and Judaism” as beginning with Theodosius I. None of the Christian emperors was actively pro-Jewish, but, as the edicts of Theodosius I demonstrate, the law could still come down in their favour if it was politicaly expedient to do so. However, the underlying negative tendency could only get stronger the more the emperor in question was prepared to concede to the growing self-assurance of Christianity as its influence spread throughout the empire.
Shäfer, The History of the Jews in the Greco-Roman World (London: Routledge, 2003), 186.