In the exercise of sovereignty, the actions of States can result in transboundary pollution, impacting other States that have limited ability to address environmental issues across borders. This situation invokes the tension between the ecological reality of our interconnected world and the political structures of international governance, which includes the development of international law. In exploring this issue, this chapter discusses how a study of issues surrounding traditional transboundary pollution can be broadened to one framed by the trade-environment nexus in international law. It argues that transboundary pollution should be seen not only through the simple and longer-established lens of environmental harms that are traceable physically from one country to another. Instead, this chapter discusses approaches that consider the less visible links of economic interdependence. Global law approaches considering the national law of the States involved and actors below the level of the State are necessary. The chapter concludes with some observations on the general principles that may apply to transboundary pollution, particularly with regard to ASEAN in dealing with the recurrence of forest fires and haze pollution in Southeast Asia.

The legal requirements governing State responsibility for transboundary pollution are now well settled at international law. However, the limited number of cases involving transboundary pollution that have been decided by international courts and tribunals leaves open many questions concerning the practical application of State responsibility doctrines in this context. This chapter unpacks the elements of a State responsibility claim for transboundary pollution, focusing on those elements that pose the most complex issues in practice. These include questions concerning how to attribute the polluting actions of private entities to States, the content of States’ obligation to act with ‘due diligence’ in the prevention of transboundary harm, and methodologies for proving the causation of injury through transboundary pollution. The chapter illustrates these questions by drawing on the example of transboundary air pollution through the emission of greenhouse gases contributing to climate change.

Freshwater disputes between States are increasing, due in part to shrinking supplies of water relative to the human population. Pollution can reduce available freshwater supplies even further and can harm aquatic ecosystems on which humans depend. Much of the world’s fresh water is shared by two or more States. Over ninety per cent of the fresh water potentially available for human use is stored in underground aquifers. While much of this groundwater interacts with surface water, it moves slowly and can be contaminated if not carefully managed. Two global treaties regulate the problem of transboundary water pollution and State practice has developed general rules of customary international law on the subject. Governments are bringing freshwater disputes to international courts and tribunals at an increasing rate and decisions in these cases hold valuable lessons for governments as regards the use, protection and management of international watercourses.

Fresh water is an important resource for riparian countries, not only for the daily life of the public, but also for agricultural irrigation and hydroelectric power production. Clean, fresh water is also essential to the protection of the ecosystem and conservation of the river basins. With economic development, rivers have been increasingly utilised and exploited, creating crises and debate among the riparian countries regarding issues of pollution risk and environmental protection. Effective pollution prevention and control requires political willingness and cooperation and good faith implementation of specific legal frameworks at the domestic level. Among the legal frameworks established by States’ practice, the Environmental Impact Assessment (EIA) mechanism is increasingly important and necessary in regulating the use of transboundary rivers. This chapter examines the legal roles and application of the EIA principle from the perspective of international law by analysing the practice of international dispute settlement relating to transboundary rivers, with the objective of developing suggestions for pollution control measures along the Lancang–Mekong River by the riparian countries in the context of the rapid development of the hydropower industry.

Transboundary pollution of the marine environment is caused by human activities conducted in and on the oceans. This chapter examines the responsibilities owed by States to ensure that damage to the marine environment caused by such activities is prevented, reduced and controlled. It explores potential remedies available to States that have been affected by transboundary marine pollution, and the ways in which liability for damage can be attributed to States who fail to give effect to their duties and obligations to protect and preserve the marine environment from activities conducted under their jurisdiction and control. The fact that the 1982 United Nations Convention on the Law of the Sea (UNCLOS) is a universally accepted global convention governing the oceans makes transboundary marine pollution different in three important respects. First, the principles and provisions governing the protection of the marine environment are more specific than those in other areas. Second, the rules in UNCLOS on the responsibility of States for internationally wrongful acts give injured States the right to seek remedies to prevent transboundary pollution of the marine environment. Third, the dispute settlement regime in UNCLOS allows States to institute compulsory proceedings against other States and hold them accountable when they fail to meet these obligations.

The 2009 Montara offshore oil spill and its consequences were anything but expected. Originating from an offshore well in the Timor Sea 140 nautical miles off the coast of Australia and 50 nautical miles from the exclusive economic zone (EEZ) boundary with Indonesia, it is a quintessential example of transboundary pollution from offshore activities and is still the subject of unresolved and heated debates between Australia and Indonesia. This chapter first briefly examines the circumstances of the Montara blowout and spill, the extent of its transboundary effects and the conclusions from the investigations carried out by Australia. The remainder of the chapter reviews the administrative and legal mechanisms and steps taken by the government of Australia and PTT Exploration and Production Australasia (PTTEP-AA), the oil operator, and their compliance with international law. It distinguishes three successive phases: firstly, the oil spill preparedness; secondly, the oil spill response; and thirdly, the mechanisms for compensation. For each phase, the factual, administrative and legal circumstances of the Montara spill are contrasted with the applicable international legal framework.