Kennedy took a fascinating approach to discussing fundamental rights in Obergefell, making an argument that combined substantive due process with equal protection. To do this, he moved away from “privacy,” used in many of the cases he cited, to “dignity” and “liberty.”
Using the term “liberty” instead of “privacy” (as in Griswold and Roe v. Wade) when discussing issues of autonomy is a good rhetorical/political move, I think, since it is, after all, specifically in the Constitution. (That courts used privacy instead is, I’d argue, because we’re a common-law country and the precedent was useful).
Using “dignity” is even more fascinating (Thomas’ dissent completely misunderstands it, I should note). Its use takes me back to Warren and Brandeis’ 1890 article on the right to privacy, which arguably attempted (with mixed success) to import a European style “dignity of the person” into American law, albeit under the concept of “inviolate personality.”
That attempt, involving restricting press invasions of the privacy of upper-class Bostonians, would run into with the First Amendment’s speech protections, but using the concept in substantive due process and equal protection analysis mostly sidesteps issues of freedom of speech–and provides a potentially powerful lens for framing the harm caused by violations of liberty in a useful and compelling way.
For more on this from this from other perspectives, see: