Restricting the liberty of persons who can be held morally and legally responsible for their conduct on the ground that they might abuse that liberty and commit criminal acts is both suspect and ubiquitous. Laws that restrict the ownership of guns, explosives, and other materials out of fear that those materials will be put to illegal uses are examples of such restrictions. So, too, are restraining orders, no contact orders, and the like. Laws restricting the residency of sex offenders are another example, as are laws permitting increased incarceration on the basis of predictions of dangerousness. Detention of suspected terrorists falls into this category, of course. So, too, do the doctrines of self-defense and defense of others, which are always preemptive of a feared future attack, as is a defensive preemptive military strike. And it may be the case that various inchoate crimes, such as conspiracy, are less examples of culpable acts than examples of acts that bespeak future danger, so that their punishment is really preventive rather than retributive. Finally, if any of these preemptive restrictions are in principle justifiable, what probabilities must be assigned to the feared conduct, and if that conduct occurs, to the feared harm, to justify the preemptive restrictions? This is an undertheorized and largely unaddressed issue in the extant literature.
This is the topic that a distinguished group of scholars discuss and debate in the pages that follow. The importance of the topic and their contributions to it cannot be overstated
