Because the laws established by the voice of the people have become corrupt and most of the people evil, Nephi decides to give up the judgment-seat, and he and his brother Lehi devote themselves to preaching.

Helaman 5:1–4

1 And it came to pass that in this same year, behold, Nephi delivered up the judgment-seat to a man whose name was Cezoram.
2 For as their laws and their governments were established by the voice of the people, and they who chose evil were more numerous than they who chose good, therefore they were ripening for destruction, for the laws had become corrupted.
3 Yea, and this was not all; they were a stiffnecked people, insomuch that they could not be governed by the law nor justice, save it were to their destruction.
4 And it came to pass that Nephi had become weary because of their iniquity; and he yielded up the judgment-seat, and took it upon him to preach the word of God all the remainder of his days, and his brother Lehi also, all the remainder of his days . . .

President Brigham Young said:

“Assuredly in the preservation of virtue, morality, and intelligence she [a nation] may look for the perpetuity of her free institutions, and the preservation of her liberty. And in the moment of her disregard of these principles, when wickedness and sin can run riot with impunity, and not moral influence and force enough be found in the people to check it, and walk it under foot, then may she reckon on a speedy downfall. . . . In the sincere observances of the principles of true religion and virtue, we recognize the base, the only sure foundation of enlightened society and well-established government. . . . That city, nation, government, or kingdom which serves not God, and gives no heed to the principles of truth and religion, will be utterly wasted away and destroyed.”

(“Discourse,” Deseret News, Mar. 1, 1855, 192.)