Is 'Internal Consistency' Dead?: Reflections on an Evolving Commerce Clause Restraint on State Taxation

This Faculty Working Paper has been updated and posted within the Faculty Scholarly Works Series. It is currently available here.


Under the internal consistency doctrine articulated by the U.S. Supreme Court under the dormant Commerce Clause, a state tax must be structured so that if every state were to impose an identical tax, interstate commerce would fare no worse than intrastate commerce. Although a relatively recent addition to the Court's Commerce Clause jurisprudence, the doctrine has played a significant role as the basis for the judicial invalidation of a wide array of state and local taxes. In American Trucking Associations, Inc. v. Michigan Public Service Commission, 545 U.S. 429 (2005), however, the Court sustained an admittedly internally inconsistent $100 per truck tax over Commerce Clause objections. The case marked a retrenchment - and arguably an abandonment - of the internal consistency doctrine as a constraint on state taxation. This article explores the implications of this decision for internal consistency analysis against the background of the doctrine's evolution over the past two decades. While observing that the decision has reconfigured internal consistency doctrine and requires a rethinking of its more expansive applications, the article concludes that the doctrine remains a significant structural restraint on state and local taxation, and it identifies the types of taxing regimes that remain vulnerable to internal consistency attack.