Positive Mathematical Programming represents a useful tool for agri-environmental policy planning. This paper estimates the consequences of the application of the Regulation (EC) 1095/2007, relating to the ban on the use of the active agent Tricyclazole, which is normally employed to combat rice blast. The main objective is to quantify the variation in farmers’ revenues and the change in use of land, in response to variations in the yield of rice produced and its production costs. The research has been focussed on the rice-farming sector in the Parco Agricolo Sud Milano (PASM), a sub-urban agricultural area of the regional capital of Lombardy that, since 1990, has been a protected area and has been under the management of the Province of Milan. The data for the case study was collected in situ and combined with the data from the Agriculture Databank of Lombardy Region considering a sample of farms representative of the rice-farming sector in the PASM. The study present the results of simulations of ten different sce-narios with a view to evaluating the overall sustainability of the cautionary measures introduced.