This chapter examines the extraterritorial application of human rights which discusses the territoriality principle and the vertical nature of human rights. International environmental law specifically recognizes the extraterritorial dimension of state action: states are under an obligation to refrain from engaging in activities that could cause transboundary harm, as pollution does not respect political boundaries. According to the Maastricht principles, “extraterritorial obligations (ETO) are a missing link in the universal human rights protection system. Without ETOs, human rights cannot assume their proper role as the legal basis for regulating globalization and ensuring universal protection of all people and groups”. The former Special Rapporteur on human rights and the environment, John Knox, has advanced the notion of diagonal rights in relation to transboundary environmental damage. According to Knox, “environmental rights are ‘diagonal’ if they are held by individuals or groups against the governments of states other than their own”.