As dissensions, crimes, and transgressions occurred within Alma’s now expanded and urbanized church, Alma turned to King Mosiah (someone he scarcely knew) to judge cases involving crimes committed by members of his church (26:10). Perhaps wanting to not get in the middle of these problems about which he had little personal knowledge, Mosiah relinquished royal jurisdiction over any such cases, even though the results could possibly involve serious consequences for his subjects (26:12).
Given authority to determine who could remain a member of the church of God, Alma took the matter to the Lord and received instructions which amount to a handbook of membership and discipline within the church (26:15–32). The key elements are well worth noting and embracing: the Lord’s repeated willingness to bless his people and their leaders (26:15–19), receiving and forgiving those who hear and know the name by which they are now and will be called at the last day (26:20–28). Alma was instructed to judge church members according to the sins they have committed, allowing them to confess, for as often as they repent the Lord will forgive their trespasses against Him (26:30). The members of the church ("ye") shall also forgive one another, but "whoseover will not repent of his sins the same shall not be numbered among my people" (26:32).
Book of Mormon Central, "Was the Book of Mormon Used as the First Church Administrative Handbook? (3 Nephi 27:21–22)," KnoWhy 72 (April 6, 2016).