Severability and the Erie Doctrine

“Severability” doctrine holds that where a statute is partially unconstitutional, a reviewing court can excise the unconstitutional part rather than declare the entire statute invalid, if consistent with legislative intent. The doctrine figures centrally in a broad array of constitutional litigation, including ongoing litigation over the “individual mandate” provision of the Patient Protection and Affordable Care Act. And the doctrine is powerful because the viability of large statutory schemes can hinge entirely on whether an unconstitutional component is severable.

But while important, severability is in many ways perplexing and underexplored. No one has come up with a fully satisfying test for determining when severance is appropriate. And no one, as far as I can tell, has critically examined choice-of-law rules pertaining to the doctrine’s application.

In an effort to resolve some of these problems, I’ve written an article that examines the U.S. Supreme Court’s approach to the choice-of-law component of severability doctrine. I contend that, in two recent decisions, the Court quietly established the severability of state statutes in federal court to be a matter of general federal common law, and that this doctrine is not only inexplicably inconsistent with dozens of cases decided since Erie Railroad Co. v. Tompkins, but also displaces a large body of diverse state law without constitutional authorization or any supporting federal interest. I argue that the new doctrine thus challenges standard accounts of the limits of federal common law and calls into question the contemporary vitality of Erie’s principle of judicial federalism. I then close by proposing an alternative that would harmonize the precedent, help to revitalize Erie, and honor the bounds of Article III judicial power.

A draft of the article is available here. Please let me know if you have any comments or criticisms; I’d appreciate any feedback, either below or at

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