The maintenance of rules is an emerging and relevant function of every kind of regulators in contemporary legal systems. If we look at history, it has always been present in order to respond to a diversity of needs, such as making rules accessible, or correcting and reforming them. Alongside maintenance in a stricter sense (the specific interventions of compilation, consolidation, revision), there is an increasing request for maintenance in order to ensure the quality of rules: it is, in fact, necessary to evaluate the effects of rules, mainly because of the fallibility of regulation. Maintenance of rules has therefore become an institutional function which completes (and no longer serves) legislation.