Criminal law scholarship is marked by a sharp fault line separating substantive criminal law from criminal procedure. Philosophical work focuses almost exclusively on the substantive side of that line, addressing adjudicative procedure (the trial process) rarely and investigative procedure (especially police conduct) almost never. Instead, criminal law theorists devote substantial attention to just two questions: what conduct should be criminal, and why is punishment justified? This essay argues that criminal law theory cannot adequately address these favored subjects—the definition of crime and the justification of punishment—without also addressing the enforcement mechanisms that link crimes to punishments. Specifically, philosophers of criminal law cannot continue to ignore the police.