Since the ratification of the Fourteenth Amendment in 1868, the Supreme Court has incrementally incorporated almost the entire Bill of Rights against the states. Scholars and jurists disagree, however, as to which provision of the amendment should be used as a tool for incorporation.

Justice Clarence Thomas, for instance, would perform the analysis using the Privileges or Immunities Clause: “No state shall make or enforce any law which shall abridge the privileges or immunities of citizens of the United States.” Note, the Privileges or Immunities Clause of the Fourteenth Amendment should not be confused with the Privileges and Immunities Clause of Article IV. In his dissent in Saenz v. Roe (1999), Justice Thomas explained that according to English common law and other legal history, “at the time of the founding, the terms ‘privileges’ and ‘immunities’ . . . were understood to refer to those fundamental rights and liberties specifically enjoyed by English citizens, and more broadly, by all persons.” In the same dissent, Justice Thomas concluded that those who lived “at the time the Fourteenth Amendment was adopted” likewise “understood that ‘privileges or immunities of citizens’ were fundamental rights.”

Justice Thomas thus rejected the Supreme Court’s 1873 decision in the Slaughter-House Cases.  In Slaughter-House, the Supreme Court held that the Privileges or Immunities Clause protected only rights “which owe their existence to the Federal government, its National character, its Constitution, or its laws.” The Court emphasized that the Clause did not protect “nearly every civil right for the establishment and protection of which organized government is instituted,” including “those rights which are fundamental.”  Justice Thomas explained that this decision “sapped the Clause of any meaning” so thoroughly that it went largely unmentioned until Saenz in 1999.

The Slaughter-House interpretation was dubious, both because it overlooked the legal history later outlined by Justice Thomas, and because it framed fundamental rights as those “which owe their existence to the Federal government” or “its Constitution.” This classification contradicts the “self-evident” truth, described in the Declaration of Independence, that “[we] are endowed by [our] Creator with certain unalienable Rights.” Thus, no fundamental rights “owe their existence to the Federal government” nor “its Constitution” because natural rights preexist government, and the government exists “to secure” them.

Nevertheless, the Supreme Court soon identified another Fourteenth Amendment avenue for incorporation, one it has continued to employ for over 120 years: the Due Process Clause: “. . . nor shall any State deprive any person of life, liberty, or property, without due process of law.”

Though practically synonymous with incorporation today, the Due Process Clause seems an odd vehicle for the task, given that its plain text only provides for a process for taking away a person’s life, liberty, or property, not a prohibition on taking away the rights once due process has been rendered. Nevertheless, the Court artificially bifurcated the Fourteenth Amendment’s Due Process Clause into procedural due process (redundant, as process is procedural) and substantive due process (oxymoronic, as substance is the opposite of process).

In United States v. Carlton (1994), Justice Antonin Scalia remarked that he did not consider substantive due process as much “a constitutional right” as “an oxymoron,” calling it “judicial usurpation” in his dissent in Chicago v. Morales (1999). Justice Thomas rebuked the doctrine in Troxel v. Granville (2000), suggesting that perhaps the Court’s “substantive due process cases were wrongly decided and that the original understanding of the Due Process Clause precludes judicial enforcement of unenumerated rights under that constitutional provision.”

With Saenz and Troxel, Justice Thomas began what some have called his “quixotic campaign” to reinvigorate the Privileges or Immunities Clause, continuing through cases such as McDonald v. Chicago (2010) and most recently Timbs v. Indiana (2019). According to Justice Thomas, incorporating the Bill of Rights against the states via the Privileges or Immunities Clause not only more faithfully adheres to the original meaning of the text, it would also better preserve the freedoms enshrined in the Constitution, as such analysis would likely be more grounded in history and tradition than substantive due process, which lacks “a guiding principle to distinguish ‘fundamental’ rights that warrant protection from non-fundamental rights that do not.”

Critics might call Justice Thomas’s hope a fantasy, as the Supreme Court seems unlikely to overturn 120 years of established precedent in one fell swoop, given the widespread legal uncertainty that would ensue. Perhaps, like incorporation itself, the revisitation of the Privileges or Immunities Clause could be performed one case at a time or in some other gradual way.

In either event, such a restructuring would require at least five Justices poised to move the needle. Thus far, Justice Thomas has pursued his crusade alone, although team membership doubled—from one to two—when Justice Gorsuch signaled his support for the idea in Timbs. While hardly a coup, this signal is nonetheless significant that more Supreme Court Justices endorse the approach than ever before.