By Thomas Z. Horton
When interpreting ambiguous punitive regulations, lower courts face a choice: either follow the Supreme Court’s instruction in Kisor v. Wilkie and defer to the enforcing agency’s typically more severe interpretation, or rely on the venerable rule of lenity — also endorsed by the Supreme Court — and adopt a less severe interpretation. This choice need not be made. Kisor deference and lenity do not clash when properly applied because these two doctrines operate at different levels of ambiguity. Lenity tips in favor of a defendant when a regulation’s meaning is subject to “reasonable doubt,” whereas agency deference applies only when a regulation is “genuinely ambiguous” — a more searching standard. Lenity, therefore, must apply before agency deference. This order of operations makes sense of both the doctrines and their justifications. Lenity’s constitutional underpinnings — in particular, the due process requirements of “fair notice” and conviction “beyond a reasonable doubt” — take precedence over the lower-order policy rationales behind agency deference.