Due Regard for Future Generations? The No Harm Rule and Sovereignty in the Advisory Opinions on Climate Change

States have long been understood to have an obligation to protect the international legal rights and interests of others, consistent with the maxim sic utere tuo ut alienum non laedas (use what is yours in such a manner as not to injure that of another). As the world's population becomes more interdependent, this no harm obligation becomes more significant. Further, as knowledge increases about the consequences of human activity for the climate and the environment, the no harm obligation takes on greater relevance vis-à-vis the interests of the Earth's future populations. Future generations’ legal interests have been recognized in the context of sustainable development and through the principle of intergenerational equity. The no harm rule requires that these interests be properly considered and addressed appropriately, commensurate with what is at stake. At a minimum, this may require avoidance of ‘manifestly excessive adverse impacts’.