In its second decision in 1941, the tribunal answered the other three questions. With respect to the second question, the tribunal stated that “under the principles of international law, as well as of the law of the United States, 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.” (page 1964)
However, not every transboundary environmental impact is to be deemed illegal under international law, save for those which entail serious or significant consequences, and can be clearly proven.
With respect to the third issue, the tribunal established framework conditions under which the Trail plant was allowed to continue operating. This included the installation of equipment to measure wind speed and apparatus to measure the sulfur dioxide content. Furthermore, the tribunal set limits regarding the concentration of sulfur dioxide in the air.
As to the fourth question of compensation, the tribunal ruled that Canada should pay compensation in the amount of $7,500 USD per year to the U.S. government if the conditions from questions two and three were not met, or if the specified limits were exceeded.
Potential takeaways for future climate migration litigation
- State responsibility and interstate claims. Though the arbitration did not concern migration, the principle(s) could potentially be transposed as an argument for state responsibility and possibly used as an interstate claim under international law, specifically the Responsibility of States for Internationally Wrongful Acts for compensation (Art. 31) or even prevention (Art. 3).
- See here for the relevance of reviving Climate Passports under this notion.
- Double-edged principle. The Arbitral Tribunal concluded that there was both an obligation of conduct and an obligation of result with the two differentiated according to the nature of the claim. The first would thus apply to the prevention of environmental damage on foreign territory, whilst the latter would apply to the compensation of damage.
- Right to compensation. The court also clarified that the implementation of preventive measures does not preclude a claim for compensation.
- The principles here were further developed in Costa Rica v. Nicaragua judgements.