Abstract
Green and blue infrastructure represents a category of nature-based solutions that serve to preserve critical ecosystem services in densely built-up environments. However, its integration is insufficiently adapted and often subject to a fragmented legal framework. This study critically examines the regulatory deficits limiting the implementation of these innovative approaches in spatial planning. It identifies the primary obstacles, namely the absence of a binding, cross-cutting definition of green and blue infrastructure across national legislations; and duplicative competences and fragmented responsibilities between vertical and horizontal public administration structures, which prevent coherent, multifunctional design. It is essential to establish binding standards for the proportion and quality of green and blue components in new development projects and to revise subsidy and financial schemes in favor of unconventional solutions. Overcoming the current regulatory inaction is a prerequisite for the transformation of cities towards a sustainable and environmentally functional structure.