The Privileges or Immunities Clause was meant to be one of the key liberty-protecting provisions of the Fourteenth Amendment. The Clause says: “No state shall make or enforce any law which shall abridge the privileges or immunities of citizens of the United States.” That sounds like a big deal, right? It’s not. The Clause has been virtually read out of the Constitution, and for people trying to vindicate their civil rights in court, it’s been of little practical use. That story—the near redaction of the Clause—begins with the Slaughterhouse Cases, which the U.S. Supreme Court decided in 1873.

More resources here: https://ij.org/sc_long_podcast/all-but-redacted-the-privileges-or-immunities-clause/