State implementation of federal law is commonplace, but has been largely ignored by the interpretive doctrines of legislation and administrative law. We have no Chevron, federalism canon, or anything else for state implementation, nor any doctrines that ask how Congress’s decisions to delegate implementation duties to states should affect how ambiguous statutes should be interpreted. For theories of federalism, state implementation raises a different question, namely, whether this “intrastatutory federalism”—an informal federalism that comes from the inside of federal statutes—is something that doctrine should protect. The prevailing functional and sovereignty accounts of federalism seem less relevant for a federalism that comes at the grace of Congress; this federalism belongs to the domain of statutory interpretation.
This Essay argues that state implementation of federal law plays many different roles, and that those differences should affect both how statutes are interpreted and how they are conceived from a federalism perspective. Sometimes state implementation effectuates traditional federalism values like experimentation, but at other times it seems to serve more nationalizing functions, like statutory entrenchment and even federal law encroachment. This variety poses challenges for legislation doctrine, because the prevailing canons of interpretation are not designed to capture such differences, and it illustrates that the broad category of cooperative federalism is more nuanced than commonly acknowledged.