The emperor is in the Church, not about the Church.
When you are at Rome, live as Romans live.
Dice have their laws, which the courts of justice cannot undo.
If you are at Rome live in the Roman style; if you are elsewhere live as they live elsewhere.
When I am at Rome I fast as the Romans do; when I am at Milan I do not fast. So likewise you, whatever church you come to, observe the custom of the place, if you would neither give offence to others, nor take offence from them.
When in Rome, live in the Roman way.