A peculiar rescript of Theodosius II, ostensibly dated between August 421 and August 423, claims to abrogate his decree of 14 July 421 that the patriarch of Constantinople should have jurisdiction over Illyricum, in satisfaction of a request of Honorius. This rescript, found in the Collectio Thessalonicensis (Vat. Lat. 5751), has remained a troubling piece of imperial legislation because the earlier decree remains both in the Codex Theodosianus (16.2.45) and the Codex Iustinianus (1.2.6) while the rescript abrogating it does not. One possible explanation for this is that upon Honorius’ death in 423 Theodosius II changed his mind and nullified his rescript. However, such an explanation fails to account for the numerous problems plaguing the document, such as anachronisms and factual inaccuracies. Whoever wrote the rescript seems to have had little knowledge about the situation of the Roman Empire at the time of its purported authorship. Furthermore, as Mommsen pointed out, the legal procedure of abrogating the decree was improper (Mommsen 1893). For these reasons, scholars have doubted the authenticity of the rescript (Chrysos 1972), although there is no fixed consensus on the matter. Still uncertain is the true purpose and date of the rescript, assuming it is in fact a forgery.
The authenticity of the rescript is dubious for many reasons. In comparing the rescript to the instigating letter of Honorius before it, it is clear that the author of the rescript was merely recycling the language of Honorius’ letter, often using the exact same phrases and only changing the person of the verbs. Given the circumstances, one would expect that Theodosius II would have put some more consideration into a reply to his uncle and imperial colleague. A closer inspection reveals further anomalies in the letter. For instance, at one point the author of the rescript mentions more than one praetorian prefect of Illyricum, even though there was only one. There are also phrases present in the rescript that were not used in the east, especially during the early fifth century. Such unawareness of the administration of the Roman Empire and unusual word choice make it unlikely that the author was a member of the imperial court.
One possible origin of the rescript is in the midst of a sixth century dispute over the patriarch of Constantinople’s right to depose bishops in Illyricum. Theodore of Echinus compiled a dossier of papal and imperial letters in 531 to present at a synod in Rome concerning the patriarch of Constantinople’s removal of Stephen of Larissa. Theodore argued that the patriarch of Constantinople had no authority in Illyricum because it was under Roman jurisdiction. To prove his case, Theodore presented over twenty documents concerning the papal vicariate of Thessalonica that demonstrated Roman jurisdiction of Illyricum. Alternatively, another possible origin of the forgery comes about during the papacy of Nicholas I (858-867), who asserted Roman control of Illyricum and sought to prove his case with corroborating documents. Among those documents were those that Stephen of Larissa had used and this presents another opportunity for the origin of the rescript, which was included in the Collectio Thessalonicensis when it was compiled in the late ninth century. In either case, the purpose would have been to strengthen Roman claims to Illyricum with the insertion of a document that abrogated the decree of 14 July 421. However, because of the peculiarities of the forgery, it is more likely that it came into being during the case of Stephen of Larissa in 531. Ultimately, this forgery reveals an alternate strategy of remedy for Christian clergy in the Roman Empire who disputed the historical validity of religious topography as the imperial government mapped it, but lacked a higher venue of appeal.