Here the 1837 edition removed the indefinite article an, replacing “into an effect” with the commonly expected English expression without the article, “into effect”. Joseph Smith is probably responsible for this change here in Alma 50:30 since the same change was marked by him in the printer’s manuscript later on in the book of Alma:
The fact that the expression “into an effect” occurs both times in the manuscript (and one is extant in 𝓞) argues that this is the intended reading in the Book of Mormon. There are no other instances of “into an effect” in the text, but neither are there any instances in the earliest text of the expected “into effect”. The critical text will therefore restore both instances of the original phrase “into an effect”.
The online Oxford English Dictionary and Literature Online have no instances of “into an effect” in either earlier or current English. I have found a number of examples of “into an effect” on , although most have been written by non-native speakers of English. The following two examples, though, appear to have been written by native speakers:
In both of these cases, “into an effect” could be due to the use of the indefinite article immediately after (“put into an effect a requirement” and “put into an effect an emergency ordinance”). In the two Book of Mormon cases, on the other hand, there is no immediately following indefinite article that could have led to an anticipatory an in “into an effect”. In any event, the phrase “into an effect” is clearly marginal in current English.
Summary: Restore in Alma 50:30 and Alma 56:30 the phrase “into an effect” in place of the expected “into effect”; although there is only a little evidence for this phrase in English, its use twice in the earliest Book of Mormon text appears to be intentional.