This chapter discusses the legal aspects of the protection of the marine environment of the deep seabed beyond the outer limits of the continental shelf, specifically its protection from the potential adverse effects caused by seabed mining. The legal framework for the protection of the marine environment from activities in the Area is contained in the LOSC, the 1994 Agreement Relating to the Implementation of Part XI of the United Nations Convention on the Law of the Sea, and the rules, regulations and procedures adopted by the International Seabed Authority (ISA). Some of these provisions specifically address protection of the environment, while others are more general but are also relevant to environmental protection. Rules for the protection of the marine environment are adopted by the ISA and implemented by the ISA itself, States sponsoring activities in the Area, and contractors carrying out such activities. This chapter describes the basic legal framework for environmental regulation of activities in the Area and the rules, regulations and procedures issued by ISA to give effect to that framework. The chapter will then discuss the way in which the regulatory system is implemented and continues to evolve through the development and application of best environmental practices as well as a focus on environmental management at regional scale. Finally, note is made of some of the issues that will require further development in the future.