Emperors Valentinian I and Valens issue a new law prohibiting government officials from having Christians appear in courts for tax purposes on Sundays.
According to the new law:
"It is Our will that no Christian shall be sued by tax collectors on the Day of the Sun (Sunday), which has long been considered holy, and by this interdict We sanction peril against any one who dare to commit this offense." [CTh 8.8.1]
So only Christians are privileged enough to be able to avoid tax courts on their sabbath, Sunday. Pagans and Jews can still be brought to court for tax purposes on any of their holy days or holidays.