91 Texas L. Rev. 543
The doctrine of “severability” permits a court to excise the unconstitutional portion of a partially unconstitutional statute in order to preserve the operation of any uncontested or valid remainder. Severability figures centrally in a broad array of constitutional litigation, including recent litigation over the “individual mandate” provision of the Patient Protection and Affordable Care Act. Nevertheless, the doctrine remains underexplored. In particular, no commentator has thoroughly examined choice-of-law rules pertaining to its application. This Article aims to fill that void. The Article contends that in recent decisions the Supreme Court has 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 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 a supporting federal interest. 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. The Article closes by proposing an alternative that would harmonize the precedent, help to revitalize Erie, and honor the bounds of Article III judicial power.