Comity is a nebulous concept familiar to us from the law of international relations. Roughly speaking, it describes a set of reciprocal norms among nations that call for one state to recognize, and sometimes defer to, the laws, judgments, or interests of another. Comity also features prominently in the law of American federalism, but in that context, it operates within limits that have received almost no attention from scholarly commentators. Specifically, although courts routinely describe duties that run from one state to another, or from the federal government to the states, as exercises in comity, they almost never rely on the term to describe or explain duties that run from the states to the federal government. The goal of this Article is to document and account for this pattern in the law of federalism. I will explore a variety of explanations for the manner in which comity floats in and out of the caselaw, including the possibility that the terminological pattern tells us something fundamental about the meaning and limits of state sovereignty in the context of our federal system.
Seinfeld, Gil. "Reflections on Comity in the Law of American Federalism." Notre Dame L. Rev. 90, no. 3 (2015): 1309-43.