Abstract
In terms of quantitative data, the Spanish Constitutional Court has, in forty years of activity (1980-2019), issued 141 judgements on environmental competences, spanning the most diverse areas this topic can cover. Within the same timeframe, the Italian Constitutional Court has issued 400 judgments on the same topic. It is self-explanatory that the Spanish and Italian Constitutional Courts’ role goes beyond the function of finium regundorum among territorial entities. Through the analysis of additional qualitative data, this article demonstrates how constitutional judgements not only regulate intergovernmental relations within specific environmental cases, but also help to shape a different institutional balance, by either exacerbating or diminishing divisive tendencies between the centre and the periphery. This fact is signalled in many ways in the case law of the Spanish and Italian Courts, from the criteria and doctrines selected to decide cases (that define relation parameters and limits between central and local authorities), to individual prominent decisions, which can dramatically alter the already sensitive interactions between State and Autonomous Communities, and between State and Regions.