Congress, Article IV, and Interstate Relations

Gillian E. Metzger, Columbia Law School


Article IV imposes prohibitions on interstate discrimination that are central to our status as a single nation, yet the Constitution also grants Congress broad power over interstate relations. This leads to the questions of whether Congress has power to authorize states to engage in conduct that otherwise would violate Article IV, and more generally of how we should conceive of Congress' role in the interstate relations context, what is sometimes called the horizontal dimension of federalism. These questions are of growing practical relevance, given recently enacted or proposed measures – the Defense of Marriage Act (DOMA) is the most prominent example – where Congress has sanctioned interstate discrimination and other state measures seemingly at odds with fundamental precepts of horizontal federalism. They also are significant on a more conceptual level, in clarifying the proper relationship of Congress and the Supreme Court in horizontal federalism disputes.

This Article contends that the Constitution grants Congress expansive authority to structure interstate relationships, and that in wielding this interstate authority Congress is not limited by judicial interpretations of Article IV. Rather than constituting unalterable demands of union, the antidiscrimination provisions of Article IV are best understood, like the dormant Commerce Clause, as constitutional default rules. These provisions are judicially enforceable against the states, but their enforceability is contingent on the absence of congressionally-authorized discrimination. This does not mean that Congress is wholly free to reset the bounds of acceptable state behavior in interstate contexts; however, the limits on Congress derive not from Article IV or principles of federalism, but instead from the Fourteenth Amendment: Congress cannot authorize states to violate interstate prohibitions that are independently protected by that provision.

Although supported by the Constitution's text and history, the real basis for such broad congressional authority lies in constitutional structure. Most of the Article is devoted to a close analysis of these standard sources of constitutional meaning to determine the appropriate parameters of Congress' role in interstate relations. The Article then closes with an examination of practical implications of the broad view of Congress' powers that it posits, assessing the constitutionality of DOMA and the currently pending Child Interstate Abortion Notification and Child Custody Protection Acts.