Within the Empire of Eboracum, the law comes from four sources, and the judgement and interpretation of law is dependant on which source contributed laws to the matter under question. The four sources of law are:
The gods are the primary provision of laws, and - by definition - their laws are the most difficult to deal with. Any recognised deity who's name is not blackened, may stand on the steps of the Templum Deorum (temple of the gods) in the forum of the city of Eboacum, and 'Speak', and their statements are taken as Holy Law.
This naturally leads to a number of contradictory laws, and one the biggest problem that lawyers and judges have to contend with is the decisions as to which of the words Spoken by a deity in this way have precedence in any given situation.
The Emperor is entitled to make decrees which immediately become law, and can only be superceded by a subsequent Imperial Decree, or by Holy Law.
Since the establishment of the External Empire, the Regens has been given the power to make Decrees which apply in the External Empire, and which may subsequently be confirmed by Imperial Decree as applying throughout the Empire.
The first decree made by the first Emperor was to establish a Senate, and give it the power to make Declarations which become law. However, those declarations can be overturned by either Imperial Decree ot Holy Law.
Senate Declarations that were in force at the time of the establishing of the External Empire also apply to the External Empire. However, an External Senate has now been inaugurated, and it is now responsible for making declarations in the External Empire. Similarly, it's Declarations will not apply to the Internal Empire.
On any matter about which there is no specific Holy Law, Imperial Decree or Senate Declaration that applies, the judgement of an Imperial Judge in that matter sets a precedent and such judgements form the foundation of Common Law. Once such judgements have been made, and the appeals process has run its full course, then the law regarding that matter is established, and can only be varied by a Declaration of Senate, an Imperial Decree, or the Speaking of Holy Law.