Michael Morley has posted this draft on SSRN (forthcoming, U Pa L. Rev. Online).  Here is the abstract:

During a recent oral argument, Justice Sonia Sotomayor raised the possibility of rejecting a proposed interpretation of a federal statute, the National Voting Rights Act, on the grounds it would have a disproportionate adverse impact on racial minorities. This Essay expands upon Justice Sotomayor’s comment, considering the possibility of recognizing a new substantive canon of statutory construction: a “disparate impact canon” that would require courts to construe ambiguous federal statutes in a manner that avoids, combats, or prevents racially disparate impacts. The Essay considers how well a disparate impact canon fits with the standard justifications for substantive canons, as well as its constitutional implications. It concludes by pointing out that debate over a disparate impact canon is a proxy for larger disputes over the proper role of judges and empathy in the adjudicative process — issues that arose during Justice Sotomayor’s confirmation hearings. Recognizing a disparate impact canon would be a natural, albeit substantial, extension of her jurisprudence.