The world’s oceans have historically been managed on the basis of geopolitically focused and legally agreed definitions which have provided the basis for national political jurisdiction. As ocean and coastal governance has evolved, the ecosystem-based management approach is now being recognized as a more appropriate intersectoral management mechanism, with strong support from the United Nations and its agencies and partners. However, this new approach to oceans management brings with it new challenges. The management of resources and impacts within LMEs represents a particularly interesting case for marine environmental law. This is due to their transboundary nature and the need to find workable and pragmatic mechanisms for management within an ecosystem which may include not only territorial waters and exclusive economic zones (EEZs) but also areas beyond national jurisdiction (ABNJ), and to deal with the challenging situation presented by extended continental shelf agreements and awards. More than ever before, there is a need for cross-sectoral and integrated dialogue and understanding within the management process at both the national level and within the regional context. Furthermore, the complexities of trying to develop effective working mechanisms for the management of high seas areas that fall within the LME and which are adjacent to EEZs (through regional cooperation and agreement) have become a matter of urgency. The concept of the ‘tragedy of the commons’ comes back to haunt such efforts with the realization that any such management of resources and geographical areas outside national jurisdiction can only be through formal consensus and agreement. The United Nations Convention on the Law of the Sea (LOSC) provides a general framework for the management of ABNJ. However, this is insufficient in the absence of agreement from those parties whose interests lie in either the direct exploitation of such areas or in the freedom to undertake potentially harmful activities in ABNJ which would otherwise be prohibited in areas under national jurisdiction. Thus, effective management at the ecosystem level can only be fully realized within the context of two possible approaches. The first approach involves a more specific and stringent elaboration and actual enforcement of the concepts embraced by the LOSC through the negotiation of a new implementing agreement. However, such agreement would need to achieve global consensus on a scale that could take years or even decades to negotiate and could still prove to be too dilute to be of any real management value. Alternately, effective ecosystem management might be achieved through the development of workable partnerships and alliances between governments, regional bodies, maritime industry and other ocean stakeholders that can arrive at a fully integrated and shared management approach leading to self-regulation. These two approaches need not be mutually exclusive, and could be both complementary and parallel. These approaches are discussed and explored further in this chapter within the context of tried and existing approaches as well as new developments and proposals.