The Book of Mormon differentiates between thieves/theft and robbers/robbery in a what that reflects its ancient background. As John W. Welch noted:
Although there is
only little difference between a thief and a robber in most modern minds, there
were considerable differences between the two under ancient Near Eastern law. A
thief (ganab) was usually a local person who stole from his neighbor. He was
dealt with judicially. He was tried and punished civilly, most often by a court
composed of his fellow townspeople. A robber, on the other hand, was treated as
an outsider, as a brigand or highwayman. He was dealt with militarily, and he
could be executed summarily.
The legal
distinctions between theft and robbery, especially under the laws of ancient
Israel, have been analyzed thoroughly by Bernard S. Jackson, Professor of Law
at the University of Kent-Canterbury and editor of the Jewish Law Annual. He
shows, for example, how robbers usually acted in organized groups rivaling
local governments and attacking towns and how they swore oaths and extorted
ransom, a menace worse than outright war. Thieves, however, were a much less
serious threat to society [Bernard S. Jackson, Theft in Early Jewish Law
(Oxford: Oxford University Press, 1972)].
Recently studies have
shown in detail how the ancient legal and linguistic distinctions are also
observable in the Book of Mormon [John W. Welch, "Theft and Robbery in the
Book of Mormon and in Ancient Near Eastern Law" (Provo: F.A.R.M.S.,
1985)]. This explains how Laban could call the sons of Lehi "robbers"
and threaten to execute them on the spot without a trial, for that is how a
military officer like Laban no doubt would have dealt with a robber. It also
explains why the Lamanites are always said to "rob" from the Nephites
but never from their own brethren - that would be "theft," not
"robbery." It also explains the rise ... of the Gadianton society,
who are always called "robbers" in the Book of Mormon, never
"thieves."
Other significant
details also emerge. It is probably no coincidence that the Hebrew word for
"band" or "bandits" is gedud, and the most famous Book of
Mormon robbers were known as Gadianton's "band." Like gedud, the name
Gadianton was spelled with two "d"s, Gaddianton, in the Original
Manuscript of the Book of Mormon....
[I]f Joseph Smith had
relied on the language of his King James Bible for legal definitions of these
terms, he would have stumbled into error, for that translation renders
"thief" and "robber" indiscriminately. For example, the
same phrase is translated inconsistently as "den of robbers" and
"den of thieves" in Jeremiah 7:11 and Matthew 21:13. The same word (lestai)
is translated sometimes as "thieves" (Matthew 27:38), other times as
"robber" (John 18:40). But there was an ancient distinction between
thieves and robbers that no translator should neglect, and over which Joseph
Smith did not blunder. ("Thieves and Robbers," in Welch ed., Reexploring
the Book of Mormon [Salt Lake City: Deseret Book, 1992], 248-49)
While reading the 1825 The Justice's Manual, we find a discussion of the law about theft at Joseph Smith's time. I am reproducing it as one might be interested to know contemporaries with Joseph Smith understood about these crimes:
Offences against the
habitations of individuals are arson and burglary. . . . Burglary
is the breaking and entering, by night, into the mansion house of another with
intent to commit a felony. The punishment of this offense is imprisonment for
life in the state prison. . . . Larceny or theft is of two kinds,
simple and compound.
Simple larceny is the
felonious taking and carrying away of the person goods of another; and is
either called grand or petit larceny, according to the value of
the goods stolen. Grand larceny consists in stealing goods above the value of
$25; and if the value of the goods stolen be $25, or under, it is petit
larceny. The punishments for petit larceny are, a fine not exceeding two
hundred dollars, or imprisonment in the county goal not exceeding three years.
The punishment for a second conviction for petit larceny, is, imprisonment in
the state prison not exceeding five years.
Compound larceny is where the stealing is from either the house or person. The felonious breaking into, or taking away goods or chattels from any dwelling house, any person being therein and put in fear, or of robbing any dwelling house any person being therein, or of robbing any person in any place whatever, are all offences punishable with imprisonment for life in the state prison.
Knowing and designedly obtaining, by false pretence, any money, goods, chattels, or other effects, with intent to defraud, &c. is punishable by fine and imprisonment, or either; and the court may sentence the offender to three years imprisonment in the state prison; and upon a second conviction, by imprisonment, not exceeding five years, in the state prison. (Thomas G. Waterman, The Justice’s Manual, or A Summary of the Powers and Duties of Justices of the Peace in the State of New York: Comprising a Variety of Practical Forms, Adapted to Cases Civil and Criminal [Binghamton, N.Y.: Morgan and Canoll, 1825], 179, 181-82)
Here are the scans of the relevant pages:
For more, see the article Book of Mormon Evidence: Thieves vs. Robbers at Evidences Central.