Emperors Arcadius and Honorius issue a new law punishing anyone who insults the Jewish leaders.
According to this new law:
"If any one dare publicly insult the Illustrious Patriarchs, he shall be subject to a sentence of punishment." [CTh 16.8.11]
There's no explanation of what exactly the punishment is supposed to be, but the Roman legal system is not known for being kind or gentle to criminals. Similar protections are not given to pagan leaders, so Jews are getting a measure of respect and protection that is not generally available to everyone.
It's worth keeping in mind also that a law like this wouldn't be issued if it didn't address an actual problem -— and a problem serious enough for the emperors of Rome to be involved in. Thus Jews in the Roman Empire must be suffering more than a bit of public abuse.