Lenity Before Kisor: Due Process, Agency Deference, and the Interpretation of Ambiguous Penal Regulations

Abstract

When interpreting punitive regulations that are ambiguous, lower courts face a seemingly stark choice: Either they follow the Supreme Court’s instruction in Kisor v. Wilkie and defer to the enforcing agency’s typically more severe interpretation, or they rely on the venerable rule of lenity—also endorsed by the Supreme Court—and adopt the 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 ambiguity thresholds. Lenity tips in favor of defendants when a regulation’s meaning is subject to “reasonable doubt,” whereas agency deference only applies when a regulation is “genuinely ambiguous”—a more searching standard. Lenity, therefore, must apply before agency deference. This order of operations makes sense both of 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.