The European Community and its member states have shared competences in marine environmental matters. That means that within their respective spheres of powers they both may act. As a consequence, they have jointly acceded to the LOSC and main marine environmental agreements and jointly participate in the work of the bodies established by these conventions. The purpose of the present study was to establish how the existence of a shared competence between the Community and its member states and the difficulty to clearly divide the respective spheres of powers impact on the implementation of their international obligations for the protection and preservation of the marine environment. Particular attention has been given to the global and regional conventions and bodies in which they jointly participate. Secondly, the research intended to establish whether the Community's regulatory action and approaches are in conformity with the existing international rules for the protection and preservation of the marine environment (hereinafter: international ocean regime), especially looking at the jurisdictional framework established by the LOSC. The material scope of the research has been limited to the prevention of oil pollution from ships, the regulation of ocean dumping and the protection of marine habitats through the establishment of MPAs. These three topics have been discussed within separate case study Chapters.