While the Maastricht Principles constitute a good basis for extraterritorial obligations regarding human rights violations arising from cross-border pollution, prescribing more punctual threshold criteria could have better reflected positive international law. The Maastricht Principles incorporate a detailed guidance as to the content of the States’ obligations to protect against human rights violations by third parties (such as private persons, corporations, other States) that set a higher standard of regulation than that required by the present state of international law as reflected in existing State practice. Therefore, they reflect a progressive development of international law especially in interpreting the obligations to protect. The Maastricht Principles however are necessarily flexible and vague as they do not provide appropriate guidance as to the threshold criteria, especially as to the minimum severity of the risk of a human rights violation and causality.