What was meant by the Fourteenth Amendment's Privileges or Immunities Clause? Did it incorporate the U.S. Bill of Rights against the states or did it do something else? In retrospect, the Clause has seemed to have the poignancy of a path not taken – a trail abandoned in the Slaughter- House Cases and later lamented by academics, litigants, and even some judges. Although wistful thoughts about the Privileges or Immunities Clause may seem to lend legitimacy to incorporation, the Clause actually led in another direction. Long-forgotten evidence clearly shows that the Clause was an attempt to resolve a national dispute about the Comity Clause rights of free blacks. In this context, the phrase "the privileges or immunities of citizens of the United States" was a label for Comity Clause rights, and the Fourteenth Amendment used this phrase to make clear that free blacks were entitled to such rights.
The incorporation thesis runs into problems already on the face of the Privileges or Immunities Clause. The Bill of Rights guarantees rights generally, without distinguishing citizens from other persons. In contrast, the Fourteenth Amendment sharply juxtaposes the privileges or immunities of "citizens" with the due process and equal protection rights owed to "any person." It therefore is not easy to understand how the Amendment's guarantee of the privileges or immunities of citizens can be understood to refer to the rights of persons protected by the Bill of Rights.
Philip A. Hamburger,
Privileges or Immunities,
Nw. U. L. Rev.
Available at: https://scholarship.law.columbia.edu/faculty_scholarship/485