The Lombardy Region approved the regulation in 2017, integrated in March 2019, which defines the criteria for compliance with the principle of hydraulic and Hydrological Invariance of rainwater, in order to reduce the flow towards the drainage networks, in a diversified manner according to of the criticality of the area in which it falls. The rapid removal of the outflows towards the receptor bodies is no longer able to meet the needs of hydraulic protection, therefore it is necessary to turn to techniques that enhance the retentive and purifying abilities of the soil-vegetation binomial. The conference aims to investigate some of the main legal issues concerning the use of green systems and infrastructures for the control, management and mitigation of stormwater runoff in urban and peri-urban areas.