This article concerns regulations written by civil servants at the French ministry of the environment. Specifically, it concerns the definition of the rules which allow implementation of the technological risk prevention plan (TRPP) which is a new land-use planning tool defined by a law of 2003. The analysis focuses on the concrete work of the rule-makers, the way they organize their actions, the difficulties they meet and the solutions they invent to solve the many problems linked to regulation writing. This immersion in the “bureaucratic factory” of regulations put the accent on certain characteristics of regulation production. Especially, it shows that this activity is not really planned and is more or less random.