Over the past thirty years, crime in Italy has plummeted: homicides, which numbered 1,938 in 1991, are now just over 300, and other crimes have also largely declined. However, the prison population has nearly doubled, and the number of life sentences has more than quadrupled, from 408 in 1992 to the current 1,867. Criminal policy has also changed radically. Even in the 1990s, the majority of Italian parliamentarians favored the abolition of life imprisonment, which the Senate voted for by a large majority on April 30, 1998. Today, all parties in Parliament reject, as a defamatory accusation, the idea of ​​being in favor of abolishing not just life imprisonment, but even the harsh prison system of life imprisonment without parole. These extraordinary changes cannot be explained except as the effects of the reduction in due process guarantees, which limit arbitrary punishment, and the decline of the culture of due process in both the political and judicial classes. Against this regression, this book reintroduces the classical model of criminal jurisdiction as the determination of legally established crimes, upon which its democratic legitimacy is based. It proposes strengthening the criminal and procedural guarantees necessary to implement this model. Finally, he argues for the need to develop a theory of criminal guaranteeism within a general theory of guaranteeism, based on the theses that most crimes are prevented by guarantees of rights and social policies, much more than by criminal policies, and that criminal guaranteeism designate the last and most unfortunate of the techniques for guaranteeing public safety from crimes and arbitrary punishments.