Imperial Court is for your most presentable form - Creatures will keep to a most presentable form as possible

Come dressed in your best and ready to impress. Walking around in hostile forms will get you kicked out of court for the evening, unless you are doing so due to a duel.

"Even the ugliest beast can be groomed and trained." 

 

Court is for courtly matters - Display of supernatural power in court is distasteful

Using supernatural powers at court is prohibited.  However, if your power is innocuous, or no one knows you have done so, or stylish and entertaining, the slight may be overlooked.

"Those who flaunt their power disappear when the truly powerful appear."

 

Status makes right: 

Superior status can enforce ones will or dictate justice

 

Nobles are responsible for everything and one they bring to court: 

“You cannot escape the responsibility of tomorrow by evading it today.”

 

Duels are meant for courtly observation

A duel must be issued, accepted, then performed in front of the court (or a good amount of the court). The Imperials must sanction the duel as well. Once done it can be to the result the challenging party desires, even death and the duel may be any style conceivable.

"Sir!  My character you have injured, and further you have insulted me in the presence of a court and large audience. I therefore call upon you as a Noble to give me satisfaction for the same."

 

War between nations cannot be declared without Imperial approval

Much like Duels, war must be sanctioned by the Imperials. Once accepted, it will be announced for all to watch and know.