Why is it an illegal setting?
If I host a Bible study in my home, that does not make my home a house of worship. If I host a party at my home, it doesn’t make the home an event space.
If he hosts fellow Jews for prayer, that does not make his home a synagogue.
If he hosts fellow Jews for prayer, that does not make his home a synagogue.
Look at his house and the rest of the neighborhood and tell me there isn’t a zoning violation there. What he has done is nothing like the occasional party, bible study or poker night. As I’ve said, I wouldn’t care if they were quiet and didn’t block the street, but the city is obligated to enforce its zoning laws.