This paper aims to analyse the path of administrative jurisprudence on how the principles of
prevention and precaution behave, the role they assume for the public decision-maker and the
judge's review. In this perspective, priority is given to examining the nature and ratio of the two
principles, as well as the relationship between them. It is then necessary to define their sphere of
operation and the essentially “methodological and bidirectional” dimension in which they move.
They, in fact, offer rules for proceeding and not for deciding, thus allowing the identification of the
path of proceduralisation of public decisions in situations of danger (prevention) or in situations of
risk (precaution), enabling the minimisation of risks, respectively, through intervention on the
causes of the possible emergence of danger and through the identification of the solution that
makes it possible to balance the minimisation of risks with the maximisation of benefits. In an
emergency phase, as in the case of compulsory vaccination, this may require operating in a
“counter-intuitive” manner with the imposition of instruments-therapies- that ensure more
benefits than risks, since the potential risk of an adverse event for an individual is far less than the
actual damage to society as a whole. In all these hypotheses, the scientific basis represents a
guarantee of the reasonableness of the choices, since the public decision-maker's assessment
must be based on acquisition of the best science of the moment and on the rigour of the relevant
method; a “reserve of science” whose reasonableness and proportionality is subject to the
administrative judge's review.
