It's true that you are a colleague
I knew about the Liber Augustalis, but still I would distinguish between the early "civil law" (maybe it could be labelled in game as jus commune) and the post Napoleonic civil law. In the medieval conception (correct me if I am wrong) the king is mainly seen as a rex iudex more than as a legislator, the final appeal. Their powers are exercised mostly through adjudication than codification. For the same reason we all remember specifically those few kings that codified law: it was an exceptional action. My point is that the concept of 'codex' and 'codification' is quite different across from the ages. Finally, the essential traits of modern civil law are 1) written law prevails over customs; 2) a new written law automatically overrules an incompatible old law. I would say that most European polities in 1337, due to how far the king was and the lack of jurists, used to apply local customs before statues. Also, it was still up to debate if a law of the king incompatible with "higher" norms (i.e. against religious norms, canon law or a long establishment provision of Justinian; but it will take time before defining a hierarchy of legal sources ) was to be respected. I think that Gregorius VII even authorised subjects to rebel against tyrants who violated canon law (that is, who didn't obey him). Btw, I study economic law and it has been sometimes since I delved more on systemic and historical aspects, perhaps I will see where your vision will lead you and then come back with more grounded suggestions). Also, my professor of legal history was a true papist, his course was all on Dante's De monarchia, so I may underestimate the power of the king before Bodin Thanks for engaging in some scholarly debate.
The Early and High Medieval rulers were seen more as judges than as legislators, that's correct, although not always (e.g. Anglo-Saxon kings started developing their own set of legal acts already in the 10th century, before the Danish and Norman conquests). However, the Reception marks the milestone after when medieval rulers started acting and being regarded more actively as legislators. Let's put an example from the
Siete Partidas, one of those 13th-century legal codes, ordered by Alfonso X of Castile c. 1256. In the First
Partida (book), the first title, law 12, '
Who has the power to make laws', clearly estates: 'Emperor, or king can make laws over the peoples of his lordship, and no other has the power to make civil laws: except, if it would by their permission. And those made in a different way, don't have the name or the force of laws, and shouldn't have value at any time.' And, regarding the legal order of precedence, in 1348 King Alfonso XI established in the 'Ordenamiento de Alcalá' how it should be in the Crown of Castile: First, royal acts, as those granted in that
Ordenamiento (Statute); then, the different written
fueros (custumes) already in place, or granted by future kings; in third place, the Siete Partidas, where neither a disposition of an
ordenamiento or fuero would be in place; and, finally, the king had final interpretation over any matter in case of doubt or silence among the precedent legal sources. That means that the ruler would have the first and last word in the act of legislation. And something important, regarding
fueros: either if they were regional, local, or estate ones, they had to be granted by the king on a written disposition, or otherwise, they wouldn't be considered valid. This was only applied to Civil Law, of course, as Canon Law was different (and even with that, the
Primera Partida is basically a civil-canon compendium, establishing the relationship between both types of laws).
As a final note, 'Civil Law' may still be better than 'Ius Commune' as a game concept, as it may not be confused with 'Common Law', which is a different concept.
