When I studied Constitutional Law some 40 years ago, the Slaughter-House Cases (1873) warranted scarcely a footnote. The scholarly consensus—including Raoul Berger's Government by Judiciary (1977)—was that the “privileges or immunities” clause of the 14th Amendment had properly (or at least definitively) been relegated into oblivion, and hardly anyone mourned its demise. Instead, most academic interest focused on other language from the 14th Amendment—in particular the terms “due process” and “equal protection”—and on the Supreme Court's mischievous use of those provisions to constrain the states' exercise of their police powers, through the “incorporation” doctrine and “strict scrutiny” analysis.
No one, save perhaps a few libertarians (notably Roger Pilon), regarded the Slaughter-House dissenters as having made a persuasive case. As the majority noted, the dissenters' open-ended interpretation—a harbinger of the Lochner era yet to come—would make the Court a “perpetual censor upon all legislation of the States,” effectively negating the concept of federalism and making federal judges (who were still regarded with suspicion in the wake of Dred Scott) the ultimate arbiters of public policy throughout the nation. This conclusion—in 1873 and until fairly recently—was considered preposterous.