Courts often hold legislation unconstitutional, but nearly always only part of the statute offends. The problem of partial unconstitutionality is therefore pervasive and persistent. Yet the exclusive doctrinal tool for dealing with this problem--severability doctrine-is deeply flawed. To make matters worse, severability doctrine is purportedly necessary for any workable system of judicial review. The accepted view is that severance saves: A court faced with a partially unconstitutional law must sever and excise the unconstitutional provisions or applications so that the constitutional remainder can be enforced going forward. Absent severance and excision, a law must fall in its entirety. This excision-based understanding of judicial review is supposedly traceable to Marbury v. Madison. In fact, this attribution is anachronistic. Moreover, the prevailing view is wrong about the distinctive function of modern severability doctrine, which is not to save, but to destroy. This Article retrieves the original approach to partial unconstitutionality and develops a proposal for implementing a version of that approach. The proposal, displacement without inferred fallback law, is simultaneously ambitious and modest. It is ambitious because it proposes a shift in the general framework for judicial review in every case; it is modest because the proposed shift would change case outcomes in only a small set of highly consequential cases.
Kevin C. Walsh, Partial Unconstitutionality, 85 N.Y.U. L. Rev. 738 (2010)