The Gist: The Louisiana Government passed legislation creating a monopoly in the slaughterhouse business for one company. Butchers brought suits against this legislation, arguing it violated their 14th amendment rights by depriving them of property without due process of law, denying them equal protection of the laws and violating their privileges and immunities as citizens. The Supreme Court disagreed and allowed the monopoly to continue, holding the 14th amendment was only intended to protect former slaves.
The Details: This was one of the first post-Civil War cases heard by the U.S. Supreme Court dealing with the newly adopted 14th Amendment. Among other things, the 14th amendment states:
No State shall make or enforce any law which shall abridge the privileges or immunities of citizens of the United States; nor shall any State deprive any person of life, liberty, or property, without due process of law; nor deny to any person within its jurisdiction the equal protection of the laws.
In essence, the butchers argued the state's created monopoly violated the 14th amendment because it gave a small number of citizens superior privileges than other citizens, deprived them of their property (i.e. their trade as butchers and their way of making a living) without due process and created unequal protection of the laws.
Unfortunately for the butchers, the Supreme Court did not interpret the 14th amendment so broadly. To the contrary, the court stated the sole purpose of the amendment was to protect former slaves from discrimination. This is an extremely controversial interpretation, as the amendment clearly states "no person" shall be denied equal protection or deprived of property without due process--the amendment does not designate these protections to a specific race or type of people. Had Congress intended only to protect former slaves with the 14th amendment, it is very likely its choice of words would have been far narrower than the words Congress actually used.
Additionally, the court stated the "Privileges and Immunities" Clause did not apply to state laws or act as a way for the federal government to police state laws. This part of the decision not only directly conflicts with what the "Privileges and Immunities" Clause actually states, but effectively rendered the clause completely useless and devoid of any teeth. Most scholars today agree that the clause--and the 14th amendment as a whole--was clearly designed to limit and police state governments.
Today, it is clear that though the 14th amendment came as a result of slavery, the purpose of the 14th amendment was to protect far more than a state's discrimination against one race. It is now well understood the purpose of the 14th amendment was to protect a variety of fundamental rights of citizens composed of all races, sexes, religions or otherwise, as well as to prevent a state from overreaching its power. In fact, later Supreme Court decisions would confirm the Slaughter-House decision was wrong. Similar to Dredd Scott, many legal scholars agree this was one of the most illogically reached decisions in U.S. Supreme Court history.