  Now almost three decades since its seminal Chevron decision, the Supreme
Court has yet to articulate how that case's doctrine of deference to agency
statutory interpretations relates to one of the most compelling federalism
issues of our time: regulatory preemption of state law. Should courts defer to
preemptive agency interpretations under Chevron, or do preemption's federalism
implications demand a less deferential approach? Commentators have provided no
shortage of possible solutions, but thus far the Court has resisted all of
them.
  This Article makes two contributions to the debate. First, through a detailed
analysis of the Court's recent agency-preemption decisions, I trace its
hesitancy to adopt any of the various proposed rules to its high regard for
congressional intent where areas of traditional state sovereignty are at risk.
Recognizing that congressional intent to delegate preemptive authority varies
from case to case, the Court has hesitated to adopt an across-the-board rule.
Any such rule would constrain the Court and risk mismatch with congressional
intent -- a risk it accepts under Chevron generally but which it finds
particularly troublesome in the delicate area of federal preemption.
  Second, building on this previously underappreciated factor in the Court's
analysis, I suggest a novel solution of variable deference that avoids the
inflexibility inherent in an across-the-board rule while providing greater
predictability than the Court's current haphazard approach. The proposed rule
would grant full Chevron-style deference in those cases where congressional
delegative intent is most likely -- where Congress has expressly preempted some
state law and the agency interpretation merely resolves preemptive scope --
while withholding deference in those cases where Congress has remained
completely silent as to preemption and delegative intent is least likely.
