What problem did the supreme court deal with in their decision in the slaughterhouse cases? apex?

Due Process Clause.

The Slaughterhouse Cases involved a legal dispute that resulted in a landmark U.S. Supreme Court decision in 1873 limiting the protection of the privileges and immunities clause of the Fourteenth Amendment to the U.S citizens. The Fifth Amendment and the Fourteenth Amendment to the United States Constitution prohibit governmental deprivations of life, liberty, or property, without due process of law.