Activists and scholars have often complained that the American criminal justice system makes choices about criminalization and sentences based on nefarious reasons. For instance, critics have claimed that criminalization and sentencing decisions are made to provide cheap prison labor to the government or private industry, to boost the private prison industry, to offer employment in rural communities in the form of jobs managing correctional facilities, or to empower police to harass undesirables and remove them from public spaces. These accusations are very alarming, and the evidence may not confirm activists’ worst suspicions. But, supposing the extraordinary evidence could be adduced, what difference would it make in a court of law? While most can agree that officials act wrongly if motivated by these concerns, it is less clear whether such officials act illegally. Does constitutional law disclose any legal ground for opposing action taken for these nefarious purposes? This Article outlines a strategy that courts might adopt for finding that some governmental purposes are, constitutionally speaking, forbidden purposes. Purpose-based arguments for invalidating government action are not entirely new. Rational basis review, familiar from the Equal Protection and Substantive Due Process contexts, sometimes requires courts to determine whether governmental action advances legitimate purposes. However, such scrutiny lacks general elucidation, and few have endeavored to elaborate how this would work specifically in the criminal sphere. This Article is a first attempt to develop a method for distinguishing the legitimate from the forbidden purposes in criminal law and beyond. On the proposed framework, courts would consider the constitutive rules of liberal legal systems, that is, those rules that both define and govern liberal legal systems. The set of constitutive rules will limit the state’s pursuit of certain aims, and those foreclosed options are, on the proposed framework, forbidden purposes under rationality review.
