Roman emperors Gratian and Theodosius I issue a new decree clarifying earlier laws regarding Christians who convert to another religion: they lose the right to make wills. Manichaeans, followers of the Persian prophet Mani, can only will property to close relatives or to the government, and their leaders will be subjected to harsh punishments.
This new Roman decree states:
"By denying them the right to make testaments, We avenge the criminal act of Christians who turn to altars and temples. The disgraceful acts of those who disdain the truth of Christianity and pollute themselves with Jewish contagions will be punished too.
Those who frequent the nefarious retreats and wicked seclusion of Manichaeans must be pursued constantly and forever. The leaders of this perversion, who have distracted unstable minds to adopt their ideas, will be punished as well but even heavier penalties will be imposed on the nefarious deceivers of this crime. ..." [CT 16.7.3]
For the wealthy elite of Rome, as in any other age, the ability to will their property to adopted children, close relatives, and friends is a means to transfer significant social, political, and economic power. Denying this to people who convert from Christianity to some other religion represents a powerful disincentive for such conversion. Thus once the head of a family converts to Christianity, it will be difficult for anyone in that family to ever change back.
Since the only religion a wealthy Roman elite is likely to convert to is paganism, this also means creating a significant disadvantage for paganism and pagan religious institutions.