This chapter examines the external affairs power. Section 51(xxix) of the Australian Constitution grants the Commonwealth Parliament power to make laws with respect to ‘external affairs’. The external affairs power has three key components and is both a subject-matter and purpose power. The external affairs power empowers the Commonwealth to make laws with respect to the subject-matters of: (1) international relations; and (2) matters geographically external to Australia. The external affairs power also empowers the Commonwealth to make laws for the purpose of: (3) implementing Australia’s international legal obligations. The power has enabled the Commonwealth to regulate matters as diverse as aviation safety standards, racial discrimination and terrorist activity.

This chapter identifies eight elements of the principle of common heritage of mankind (CHM) in the context of DSM, which exhibits a delicate balance between development and conservation. Environmental protection is an integral and inherent restrictive element of CHM. The chapter reflects preliminarily upon environmental protection in DSM at the conceptual and operational levels. At the conceptual level, it argues for an erga omnes character of international environmental obligations. Such a characterization would make a big room for innovative practices with respect to a more informative, inclusive and transparent model of global environmental governance of DSM as well as have legal implications on the question of who is entitled to invoke liability of the contractor, the sponsoring State and the ISA for environmental damage. At the operational level, it highlights the significant role of marine sciences and the fact that the great gaps of current marine scientific knowledge constitute a fundamental restraint to the development of DSM as well as the environmental protection in DSM.