In the Trail Smelter case, United States vs. Canada, the Court held that:

Under the principles of international law ... no State has the right to use or permit the use of its territory in such a manner as to cause injury by fumes in or to the territory of another or the properties or persons therein, when the case is of serious consequence and the injury is established by clear and convincing evidence. 1

This case was heard close to a century ago, yet little has developed in terms of states' obligations or responsibility for transnational effects of their actions. This is true for international law generally, and for international human rights law more specifically.