Helaman 4

As Mormon writes the history of the church and the democracy of the Nephites, he teaches the consequence of their actions -

"Now this great loss of the Nephites, and the great slaughter which was among them, would not have happened had it not been for their wickedness and their abomination which was among them; yea, and it was among those also who professed to belong to the church of God.
12 And it was because of the pride of their hearts, because of their exceeding riches, yea, it was because of their oppression to the poor, withholding their food from the hungry, withholding their clothing from the naked, and smiting their humble brethren upon the cheek, making a mock of that which was sacred, denying the spirit of prophecy and of revelation, murdering, plundering, lying, stealing, committing adultery, rising up in great contentions, and deserting away into the land of Nephi, among the Lamanites—
13 And because of this their great wickedness, and their boastings in their own strength, they were left in their own strength; therefore they did not prosper, but were afflicted and smitten, and driven before the Lamanites, until they had lost possession of almost all their lands." (Book of Mormon | Helaman 4:11 - 13)

Now having lost their democracy, freedoms and land, the Nephites then -

"...saw that they had been a stiffnecked people, and that they had set at naught the commandments of God..." (Book of Mormon | Helaman 4:21)

This is a great warning to our day for -

"...they had altered and trampled under their feet the laws of Mosiah, or that which the Lord commanded him to give unto the people; and they saw that their laws had become corrupted, and that they had become a wicked people..." (Book of Mormon | Helaman 4:22)

Note that the laws of Mosiah were the laws of God much like I believe the constitution of the United States at one time was according to the laws of God for -

"According to the laws and constitution of the people, which I have suffered to be established, and should be maintained for the rights and protection of all flesh, according to just and holy principles;
78 That every man may act in doctrine and principle pertaining to futurity, according to the moral agency which I have given unto him, that every man may be accountable for his own sins in the day of judgment.
79 Therefore, it is not right that any man should be in bondage one to another.
80 And for this purpose have I established the Constitution of this land, by the hands of wise men whom I raised up unto this very purpose, and redeemed the land by the shedding of blood." (Doctrine and Covenants | Section 101:77 - 80)

And because the Nephites had corrupted thier law to justify their carnal desires for wickednes (power, materialism, immorality) -

"...because of their iniquity the church had begun to dwindle; and they began to disbelieve in the spirit of prophecy and in the spirit of revelation; and the judgments of God did stare them in the face.
24 And they saw that they had become weak, like unto their brethren, the Lamanites, and that the Spirit of the Lord did no more preserve them; yea, it had withdrawn from them because the Spirit of the Lord doth not dwell in unholy temples—
25 Therefore the Lord did cease to preserve them by his miraculous and matchless power, for they had fallen into a state of unbelief and awful wickedness..." (Book of Mormon | Helaman 4:23 - 25)

"...thus had they fallen into this great transgression; yea, thus had they become weak, because of their transgression..." (Book of Mormon | Helaman 4:26)

What a important warning to us in our day!