Legal: Mormon tells us two important pieces of information about the Nephite legal system. The first is that there the realm of law did not attempt to restrict belief. This is fairly obvious in the land of Zarahemla where the church has now become a subset of the overall culture rather than representing the entire culture. This situation has allowed both dissent and the rise of cities like Ammonihah which were followers of the order of Nehor, yet part of the Nephite hegemony.
The second piece of information is that the law of the land was related to a scriptural basis. We do not know whether or not this justification by scripture (referring to Joshua 24:15) was part of the Nephite codification of law, or whether or not it is an interpretation by Mormon. Regardless, the idea that scripture might serve as the basis for civil law is certainly permitted by Mormon’s culture, and it is not unreasonable to suppose that it would have similarly been available to Alma, and to Mosiah (deemed the lawgiver – see Alma 11:1 as an example).
The method of creating a scriptural basis for the law is interesting. The scriptural text defines a specific instance where a prophet declared that others had a right to choose. That right was not legalistic, but rather pragmatic in the episode in Judges. Nevertheless, the principle of choice was selected from that text, and the pragmatic principle was expanded to a legal principle. The law is both an expansion and formalization of the scriptural episode. A single episode becomes a model, and then a formal, legal model for social actions.
This is by no means an unusual way of formulating law. For instance, we find the following in the Dead Sea Scrolls:
4Q271 Frag. 1 Col. 1 ’[...] with silver […] […] and the year of [jubilee] shall arrive [… ] [… ] no one should abandon […] […] for it an abhorrent thing; and the verse that says [… … “if you buy from] your neighbor, do not defraud him” (Lev. 25:14). Now this is the meaning [… ] [… he must be frank about] all that he is aware of that is found [in whatever he is selling;] [if there is a fault in it] and he is aware of it, he is cheating him, whether it is human or animal. And if […] to betroth, he shall tell him about all her defects, lest he bring upon himself the judgment of [the curse, which says, “Cursed] is he who leads the blind astray on the road” (Deut. 27:18). Moreover, he should not give her to someone who is not proper for her, for this [is a case of ’forbidden mixtures" … like plowing with] an ox and ass, or clothing made of wool and flax together. (Wise, Abegg, and Cook. The Dead Sea Scrolls. A New Translation._ HarperSanFrancisco, 1996, p. 63).
In particular, note the expansion of the meaning of Deuteronomy 27:18. The writer of this particular scroll is basing regulation on statements from scripture, and applying the scripture in new contexts for new laws, precisely the process we see in this Book of Mormon text.