The “rule of lenity” “requires ambiguous criminal laws to be interpreted in favor of the defendants subjected to them.” Although long a favorite of defense attorneys, actual applications of the rule, at least at the Supreme Court level, have been relatively rare. This is perhaps somewhat surprising as the rule’s roots in due process principles, and potential application where a strict construction of a statute results in an ambiguity, could lead both traditionally liberal and traditionally conservative Justices to favor its use. In 2008, in United States v. Santos, the Supreme Court issued a plurality opinion holding that a key term in a federal money laundering statute was ambiguous and applied the rule of lenity to resolve the ambiguity in the defendants’ favor. The plurality involved just such a coalition of conservative and liberal Justices (Justices Scalia, Thomas, Ginsburg, and Souter; with Justice Stevens writing separately and agreeing that the rule should apply), raising the question of whether the rule may be entering a period of somewhat greater application...