The Law of Anthemius states that Julia married someone "who had been a slave of her own household," and given our knowledge of mater familias and the fact that it was Julia herself who had come forth before the emperor, it is possible to speculate that Julia was the head of her own household.
Although Julia was presumably a member of the upper class, she did not have a male relative in the Senate at the time; therefore, neither Julia nor anyone in her household, including her freedman, possessed political power that could be wielded against Anthemius, and he could allow by his "imperial grace" for the declaration of her marriage as legal.
The emperor Anthemius was a special case, and he saw Julia's situation as a political opportunity when he needed one.
Notably, the law lacked any mention of freedmen and marriages between freeborn women and freedmen from the time it was first enacted until Anthemius passed his legislation in 468 CE.
Constantine's legislative practices were important because, like Augustus and previous Roman emperors before him, he set the example that Anthemius would follow for his own legislation in order to make an impact on Roman morality and to fulfill the duties of a Roman emperor.
Within the Law of Anthemius, the emperor was equipped with the precedents of the past; he prohibited marriage between free women and freedmen, and he set the punishment for violating his new law at property confiscation and deportation for free women and enslavement of their children.
In addition to his political motive, Anthemius may have had another motive behind the law that focused on the many freedmen who were part of the imperial household and could be swayed by wealth and status.
The aristocracy's concern with slaves and their relations to slaves allowed Anthemius to make these preoccupations a focus of the law, using the place of slaves in Roman society to communicate a larger objective: forging his image as a Roman emperor.
Leo, Anthemius, Zeno, and Extraordinary Senatorial Status in the Late Fifth Century.