Hi there. Recently, I was having a conversation with my brother who's studying constitutional law. We were wondering why Louisiana which was acquired from France in 1804 as a territory kept its Napoleonic code whereas the states acquired after the Mexican cession have a full common law code like the other states. I would imagine that like in the former Mexica territories civil law was practiced as well.
So why was Louisiana allowed to keep its civil law system whereas other territories that also practiced civil law started using common law after their incorporation. Was Louisiana more settled than the west making it more difficult to replace a law system?
Edit: Mexico instead of Louisiana.
Based on the accounts I’ve seen of the Mississippi territory, I’d surmise that this is largely due to the circumstances surrounding Louisiana’s acquisition, namely that it was probably not within an Anglophonic sphere of influence before acquisition.
During the formative years of the Mississippi territory, many places there were acquired through conflict by the British before being acquired as a result of the revolution and subsequent expansion. When this happened, the conquering party often instituted their legal systems as a matter of course. When Britain acquired Mobile, for instance, the commandant immediately implemented British common law. Even though Spain would later take Mobile, residents of this area were chiefly Indian traders. The Creeks wanted cheap and durable British goods, so trade with British firms further concreted British (and later American) culture.
Land within this area that was ceded from Spain to the US was already within the US sphere of influence, which can be seen from the tenuous situation at Fort Tombeckbe due to the conflicting claims of Spain and Georgia and the continuous influx of American citizen-settlers.
Until cession to the US, Louisiana was never within that sphere of influence. In fact, Spanish and French acculturists would migrate to New Orleans when their communities became untenable or oppressive, such as the French leaving Mobile after the seven years’ war or the French leaving Demopolis after the failed vine and olive colony.
Source: mostly Alabama: the history of a Deep South State, Rogers, Ward, and Atkins.