Most people who think they are law-abiding probably are not. While they think of themselves as obeying the law, most are probably routine committers of penumbral crimes; defined as people that are persistent violators of criminal prohibitions not ordinarily stigmatized or subjected to social or legal sanction at the levels where prohibitions are routinely violated. In their view, and the view of most of society, these offenses are not blameworthy at the level where the legislature has set them, thereby resting in a penumbra of technically sanctionable but widely permitted conduct. This article argues that there are several reasons to be concerned about the phenomenon of penumbral crimes. The article is divided into four sections. The first section sets out the criteria which characterize a penumbral crime and applies the criteria to one paradigm example: speeding. Section II explores the reason penumbral crimes develop, relying on the literature of social norms theory. Section III critiques the use of traditional criminal statutes for penumbral crimes, arguing that they run the risk of establishing a new norm of law violation and impose costs not on law violators but on law observers. In the final section, alternatives are explored to the existing regime of penumbral crimes. The principle advantage of the penumbral crimes phenomenon is that it creates an opportunity for pretextual and discriminatory literal enforcement at the whim or on the hunch of law enforcement. A radical solution is proposed to alter the law so that it actually sets out the prohibited behavior, reflecting the penumbral nature of the offenses it defines. This allows the recognition of a penumbral range of permitted behavior while allowing persons engaged in those behaviors to comply with the law.