The Empire only exists for the purpose of enforcing moral law on all its territories defending its territories against outside threats and to intervene in the matters of the Empire in times of crisis.
The territories of the Empire have all the rights to decide on their own which laws they use, whom they grant citizenship to, what taxation policy they use, whether they are ruled by a prince, a bishop or a senate. The political diversity of the member states of the Empire legitimise the existence of that instution.
If the people you are ruled by are within the range of your guns, it is foreign occupation. There is no liberty in our modern republic.