Brock Lennox notes that while on the Lord's errand to retrieve the brass plates, Nephi and his brethren initially confronted Laban with Laman as their spokesman. When Laman told Laban what they had come for, Laban became angry and threw him out from his presence, saying: "Behold thou art a robber, and I will slay thee" (1 Nephi 3:13). In this circumstance the reader should note that while no robbery actually took place, Laban makes a decree which would foreshadow judgment and punishment concerning his own actions.
It seems apparent that Laban had sufficient authority at the time to decree penalties which were carried out in the larger political system of Jerusalem. While a decree of death for a robber might or might not have been justified under that larger political system, Laban's demand for this strict penalty at least represented a case of judgment according to Laban's own personal standard.
As the narrative will relate, Nephi and his brethren would return to Laban a second time bearing great personal wealth as an exchange for the plates. This wealth was probably far in excess of the value of the plates even according to Laban's worldly perspective, for upon seeing their gold and silver and precious things Laban "did lust after it, insomuch that he thrust [them] out, and sent his servants to slay [them] that he might obtain [their] property]" (1 Nephi 3:25).
Thus Laban will prove to be the very robber he had accused the sons of Lehi of being. He rejected the Lord's covenant servant in order to seek after the idolatrous god of earthly riches. Ironically, he would soon receive the very judgment he had decreed--death. "Therefore thou art inexcusable, O man, whosoever thou art that judgest: for wherein thou judgest another, thou condemnest thyself; for thou that judgest doest the same things" (Romans 2:1) "Out of thine own mouth will I judge thee thou wicked servant" (Luke 19:22). "The same judgment which ye judge ye shall also be judged" (Moroni 7:18). [J. Brock Lennox, "Analysis of Laban's Refusals to Part with the Plates," unpublished paper]