Throughout this paper, the global agreements with respect to marine protected areas will be discussed. Several regional marine instuments contain provisions on the designation and management of marine protected areas. Regional agreements are discussed. An overview of states which implemented specific law about marine protected areas are given, as well as the real state of the art: how common are MPAs? Where do MPAs exist? All these clarified with a focus on a few examples. In this international framework, the situation for the Belgian North Sea and the (legal) possibility for marine protected areas are analysed.