Although the federal government is traditionally understood to enjoy exclusive authority over immigration, states and localities increasingly are asserting a role in this field. This development has sparked vigorous debate on the propriety of such involvement, but the debate is predicated on a misunderstanding of the nature of federal exclusivity. Challenging the conventional wisdom that the Constitution precludes meaningful state and local involvement in immigration-a structural preemption argument-this Article argues that the Constitution allows immigration authority to be shared among levels of government. After establishing the correctness of this view of immigration authority, this Article argues that the constitutionality of state and local involvement should be assessed through the lens of traditional federalism values. A federalism lens does not necessarily validate any particular state or local regulation, but in lieu of the blunt tool of structural preemption, it is a far superior means for determining the proper allocation of immigration authority among levels of government and will lead to a more nuanced assessment of the interests at stake.
In Farmers Branch, Texas, the city council enacted a measure to fine landlords who rent their premises to unauthorized migrants,1 and in Arizona, the state legislature passed a law imposing stiff penalties on employers who intentionally or knowingly hire unauthorized migrants.2 In San Francisco, the board of supervisors passed a measure that bars law enforcement officers from inquiring into the immigration status of an individual in the course of a criminal investigation.3 In Alabama and Florida, state officials have entered into agreements with the federal government permitting state law enforcement officers to arrest and detain non-citizens on immigration charges.4 Other examples of non-federal involvement in immigration abound.5 Although these efforts vary in type and political orientation, increased state and local involvement in immigration-often referred to as "immigration federalism"6-is one of the most important developments in immigration policy.
The legality and propriety of immigration federalism has sparked a vigorous debate among legal scholars. The vast majority of scholars decry it. Some scholars express concern that state and local governments are more likely to engage in discrimination against noncitizens.7 Others fear that giving state and local law enforcement officers a role in the enforcement of federal immigration law will discourage non-citizens from reporting crimes8 and encourage racial profiling.9 On the other side of the debate, some scholars welcome the assistance of state and local officers as the "quintessential force multiplier," noting benefits for national security and enforcement of immigration law generally.10 Finally, other scholars acknowledge the inevitability of immigration federalism and find a potential silver lining.11
Immigration federalism also has become a central political issue of our time. Legislators at all levels of government are engaged in a rancorous debate over the propriety of immigration federalism, and the issue has led to numerous confrontations between the political branches of governments.12 As with the debate among legal scholars,13 emotions run high.14
Finally, the legality of immigration federalism is the subject of increasing litigation in the federal courts. Several lawsuits have been filed challenging state and local enactments,15 and trial courts are beginning to issue opinions.16 In these early decisions, courts are reaching conflicting conclusions.17
This debate and these initial court decisions misunderstand the nature of federal exclusivity in immigration. As a descriptive matter, the federal government alone establishes the content of "pure" immigration law-the rules governing the admission and removal of non-citizens. Courts and scholars, however, widely accept this description of federal dominance as constitutionally mandated, believing that the Constitution commits authority over immigration law solely to the federal government. …