Scholars have written volumes about the separation of powers, but they have focused on the administrative state and have wholly ignored the criminal state. Judges, too, have failed to distinguish criminal from administrative matters. So, the conventional wisdom has been that whatever theory works for the administrative state should work for anything else, including criminal matters. Because most scholars and judges have supported a flexible or functional approach to separation of powers in the regulatory sphere, they have failed to see a problem with the functional approach in criminal cases. Indeed, the Supreme Court has been even more permissive of the blending of powers in the criminal context than it has in cases involving nonpenal laws.

This Article shows why the existing functional approach to separation of powers in criminal matters cannot be squared with constitutional theory or sound institutional design. It explains that there are crucial differences between administrative and criminal matters when it comes to the separation of powers. Maintaining the separation of powers in criminal matters has strong roots in the Constitution's text and structure. Moreover, unlike the administrative law context, where agencies must adhere to the structural and procedural protections of the Administrative Procedure Act and their decisions are subject to judicial review and political oversight, the government faces almost no institutional checks when it proceeds in criminal matters. The only safeguards come from the individual rights provisions of the Constitution, but those act as poor safeguards against structural abuses and inequities. The current arrangement therefore takes the worst possible approach to separation of powers in the criminal context. The protection provided by the separation of powers is weakened, but nothing takes its place. As a result, the potential for government abuse is, perversely, greater in criminal proceedings than in regulatory matters. This Article therefore advocates more stringent enforcement of the separation of powers in criminal cases, where it is most needed. This approach would lead to different outcomes in the Court's major separation of powers cases dealing with criminal matters and would result in a rethinking of its acceptance of unreviewable prosecutorial discretion over charging and plea bargaining.