Nowadays, there is increasing evidence of the growing intensive use of the seas and oceans in parallel with the development of new activities on them as result of advances in new technologies. These is subjecting the marine environment to greater pressures and impacts, and, in turn, it is generating overlaps and collisions between different uses over the occupation of the marine space that can lead to both domestic and international tensions and conflicts. Among these new uses of the sea that may conflict with the protection of both the marine environment and other projected uses in the sea, the growing development of marine renewable energies stands out worldwide and, mainly, at the European level, in line with the objectives pursued in terms of energy and climate at the international, regional, and state level. Despite of the fact that the expansion of these technologies is subsequent to the approval of the 1982 United Nations Convention on the Law of the Sea, this, in general terms, serves as a general framework to the development of these devices at international level. However, it is nonetheless true that there are several grey areas (particularly in relation to the Exclusive Economic Zone, the extended continental shelf, and the high seas) which merit closer examination, as is conducted through this research work. Indeed, greater cooperation and coordination between the different States is required to regulate, organize, and manage marine spaces in the light of the growing development of new uses and, in particular, in order to spatially planning the implementation of marine renewable energies. Currently, at the regional level, on the European scene, this cooperation is structured mainly within the European Union and the Regional Seas Conventions (within the scope of this research work the OSPAR Convention highlights, which will be studied in comparison with the cooperation mechanisms that are established in the Baltic Sea under the Helsinki Convention). However, there are areas of uncertainty in relation to the role and competences that the European Union can develop in relation to the regulation and management of activities that are projected on the sea, as well as in terms of the compatibility between certain provisions and goals pursued by different norms that form part of the secondary EU legislation, mainly in those cases in which the objectives of protecting the marine environment and biodiversity may collide with other socio-economic targets. Both issues are analyzed to determine the effectiveness of the European Union’s actions in facilitating coordination and cooperation among Member States in planning the development of marine renewable energies. The importance of intensifying relations of cooperation and coordination between States at the bilateral and cross-border level is also analyzed with the aim of addressing specific aspects of greater local or regional interest connected with marine and coastal spatial planning. At the state level, we will conduct a study of the Spanish and Portuguese legal systems, given the geographical proximity of both countries, their long tradition of cooperation, and the high renewable energy potential (mainly offshore wind and wave power) that characterizes their marine waters. In particular, we will focus on the study of their respective domestic law on marine spatial planning and their impact on the management and implementation of marine renewable energies. Likewise, we will study the cooperation and coordination mechanisms that are applicable in this regard not only between the two countries, but also internally in each one of them, mainly between the central government and autonomous regions. Finally, as concluding observations, new ideas and alternatives aimed at intensifying cooperation across each governance (international, European regional, bilateral, and state) level will be proposed.

Key Words: Law of the sea, Environmental Law, European Law, UNCLOS, OSPAR, Marine Spatial Planning, Marine Renewable Energies, Spain, Portugal, Cooperation.