Advisory Opinions – "All About Substantive Due Process"

October 30, 2025 | Hosts: Sarah Isgur and David French

Episode Overview

In this episode, Sarah Isgur and David French devote the entire hour to a listener question: Can you destroy the best steelman of incorporation through substantive due process? Using this as a springboard, they take a wide-ranging tour through American constitutional history, focusing on the origins, development, and controversies surrounding substantive due process. Touching on landmark cases, nuanced doctrinal debates, and real-world implications, they break down what substantive due process is—and isn't—why it persists, and why it remains so hotly debated today.

Key Discussion Points and Insights

1. Why Substantive Due Process Is Newsworthy Right Now

• The episode opens with a discussion of a current Supreme Court petition stemming from Kim Davis’s request to overturn Obergefell v. Hodges (2015, the same-sex marriage case), prompting renewed media focus on substantive due process.
• David downplays the likelihood of Obergefell being overturned:

  "I would literally fall out of my chair in shock if the court took this case … but absolutely, positively, there are a lot of people who are very interested in this right now." (03:20, David French)

• The case is set for conference on November 7th, but both hosts doubt it will lead to substantive change.

2. The Steelman of Obergefell’s Vulnerability

• Sarah details why concerns about Obergefell, though likely exaggerated, are rooted in understandable legal processes, particularly since the Court asked for a response in the Kim Davis petition:

  "That alone, I think, was worth some news stories … when the Court didn’t just deny it out of hand." (05:14, Sarah Isgur)

• She explains how Obergefell was a 5–4 substantive due process decision and highlights the famous dissent by Justice Scalia:

  “If even as the price to be paid for a fifth vote, I ever joined an opinion … I would hide my head in a bag. The Supreme Court … has descended from the disciplined legal reasoning of John Marshall and Joseph Story to the mystical aphorisms of the fortune cookie.” (08:10, quoting Scalia)

3. Reliance Interests and the Respect for Marriage Act

• The hosts examine whether the passage of the Respect for Marriage Act replaces constitutional reliance interest, concluding it does not:

  "I believe the reliance interest is on the Court’s constitutional ruling, not on the current state of the law." (12:45, Sarah Isgur)
  "You can’t eliminate the reliance interest by having a belt and suspenders extra statute, given how ephemeral statutes can be compared to constitutional rights." (13:46, David French)

4. The Text, History, and Structure of Substantive Due Process

• Sarah distinguishes between the “privileges and immunities” and “privileges or immunities” clauses—often confused but textually and doctrinally distinct—and apologizes for her perpetual mix-up.

5. Foundations: Is Substantive Due Process Born in Dred Scott?

• The hosts analyze Dred Scott v. Sandford (1857), where the Court invoked due process to protect a slaveholder's property rights (i.e., owning slaves), possibly marking the first use of what would become substantive due process.
• They clarify the difference between procedural and substantive due process:

  "So this is like we all know what procedural due process is. … Substantive due process is this idea that there are some things you can't do even if you did follow the process." (18:19, Sarah Isgur)
  "What substantive due process does is sort of say it's going to identify the liberty interest and protect it to a certain degree, regardless of process." (20:16, David French)

6. Slaughterhouse Cases and the Death of Privileges or Immunities

• Detailed discussion of the Slaughterhouse Cases (1873), which gutted the privileges or immunities clause and forced courts to attach unenumerated rights protection to due process instead.
• Sarah highlights Justice Field’s famous dissent and colorfully recounts Field’s life, referencing his opposition to the Court's narrowing of the 14th Amendment.
• David notes an overlooked textual point:

  "The scope of privileges or immunities and the scope of due process are different … would that mean that noncitizens are not protected by the Bill of Rights the way they are protected plainly by the language against the federal government?" (32:32, David French)

7. The Lochner Era and Its Disrepute

• Lochner v. New York (1905) is covered as the high-water mark of the Court striking down progressive labor regulations using substantive due process to protect “freedom of contract.”
• David points out its contemporary infamy:

  "Individual liberty could be wielded in such a way as to be so brutal towards vulnerable people … It's the heir to Dred Scott in that sense, … using due process to protect activity most people today would look at as utterly appalling." (37:20, David French)

• Sarah recounts how conservatives came to dislike the Lochner era, and how FDR’s court-packing threat and the “switch in time” shifted the Court’s approach, replacing Lochner with the "rational basis" test, but creating strict scrutiny for fundamental rights.

8. Griswold, Roe, Obergefell—Liberal Revival of Substantive Due Process

• Griswold v. Connecticut (1965), with its famous “penumbras and emanations” line and the protection of marital privacy, revives substantive due process to protect progressive liberties—now to the delight of the left.

  “There’s no way to shake this out in a way that is going to make...make everyone happy … there are unenumerated rights. You can’t be an originalist and think there are no unenumerated rights, because right there in the text, it says there are.” (42:49, David French)

• The hosts point out that this approach is controversial regardless of political orientation and that later cases, like Obergefell, are drafted to avoid the explicit language of substantive due process, even as the doctrine underpins them.

9. Doctrinal Uncertainty—Does the Label Matter?

• David argues that the core uncertainty abides no matter which clause or doctrine you use:

  “We know they need to be recognized, we know they need to be protected against the states and local governments. And you have this sort of menu item...which is the line item that you’re picking to do it.” (44:01, David French)

• Ultimately, the hosts agree that arguments over which specific clause grounds unenumerated rights may feel like “angels dancing on the head of a pin,” but do have some real consequences.

10. Practical Implications and the Future

• Sarah references Judge Kevin Newsom’s law review article revisiting the privileges or immunities clause, and a 1999/2000 welfare case (Saenz v. Roe) in which the Court did use privileges or immunities to recognize the right to travel.
• Both hosts predict the Kim Davis petition will not result in Obergefell being revisited, though David believes Justice Thomas might issue a statement about privileges or immunities (50:36–51:08).

Notable Quotes & Memorable Moments

• Justice Scalia on Obergefell:

  “I would hide my head in a bag. The Supreme Court ... has descended from the disciplined legal reasoning of John Marshall ... to the mystical aphorisms of the fortune cookie.” (08:10, Scalia dissent quoted by Sarah)

• Sarah, on reliance interests:

  “I believe the reliance interest is on the Court’s constitutional ruling, not on the current state of the law ... the precedent doesn’t come back.” (12:45)

• David, on core confusion:

  "You can’t be an originalist and think there are no unenumerated rights, because right there in the text, it says there are." (42:49)

• On the end result:

  “We just know that there are … unenumerated rights. We know that they should be protected, but we don’t have the specificity. So, yes, it matters. But whether we’re talking substantive due process, privileges or immunities, Ninth Amendment, equal protection, all of it adds up to much the same thing.” (46:21, David French)

Timestamps for Key Segments

• Listener Question Introduction: 01:26
• Kim Davis and SCOTUS News Hook: 03:20
• Obergefell Steelman & the Scalia Dissent: 05:14–09:15
• Reliance Interest and Respect for Marriage End Run: 11:39–14:24
• 14th Amendment Structure & Privileges/Immunities Clause: 22:58–30:03
• Slaughterhouse Cases Explainer: 29:00–33:55
• Lochner Era Explained: 34:16–39:11
• Griswold, Roe, and Penumbras: 41:55–44:19
• Modern Doctrinal Uncertainty: 44:19–46:21
• Final Predictions for Kim Davis Case Results: 50:30–51:41

Conclusion: Why Substantive Due Process Still Matters

• The episode closes with both hosts agreeing that the controversy surrounding substantive due process is permanent: there are fundamental rights not enumerated in the Constitution, but tracing their source—substantive due process, privileges or immunities, Ninth Amendment, or elsewhere—remains “a question that’s not going away anytime soon.” (47:29)
• The central tension: judges must use judgment to identify and protect these rights, but the text does not give a clear roadmap.

Final Thoughts & Tone

The discussion is scholarly yet conversational, with Sarah and David’s wry legal humor and signature deep dives. The episode provides listeners with a panoramic understanding of substantive due process—its origins, why it divides legal thinkers, and its continuing influence in today’s most contentious legal fights. For listeners wanting an accessible but thorough grounding in this vital constitutional doctrine, this episode is a must-listen.