108 Iowa L. Rev. 1531 (2023)
Liminal immigration rules operate powerfully beyond the edge of traditional law to govern the movement of people across borders and their interactions with the immigration system within the United States. This Article illuminates this body of “liminal law,” revealing how agencies and advocates have innovated to create widely followed rules that operate like traditional legal rules but are not. These rules are law-like, or liminal, in that they stand apart from “hard” law like statutes, regulations, or judicial opinions, but exert a similar authority. Because of their liminal nature, these rules lead a precarious existence and are often in transition, tending either toward codification or toward extinction. They are nonetheless sticky, resisting their own demise. The Article employs case studies of three liminal rules—the Deferred Action for Childhood Arrivals program, the mandatory immigration detainer, and administrative closure—to illustrate the characteristics and the potency of liminal immigration law.