This thesis argues that the International Court of Justice (ICJ) is in a unique position to advance environmental norms but that it does not. Reasons for this situation are analysed and, ultimately, a biocentric natural law philosophy is presented to address the deficiencies of the Court's environmental protection. To construct this argument the thesis demonstrates that it is not unreasonable to assume that the Court’s decision-making may embody a tacit philosophy. Notions of environmental duty and the traditions of thought they may be based upon are explored to understand this. Changing conceptions of the place of humans in the world and related notions of responsibility are shown to culminate in morally neutral utilitarianism, which removed all that had limited a ruinous environmental regard. Modern environmental philosophical perspectives must be characterised as movements to different extents, away from utilitarian thinking. ICJ case analysis is conducted against these perspectives, where it is found that the Court is inconsistent and hesitant to articulate the content and status of principles of international environmental law. In response, the thesis sketches a biocentric perspective based on natural law. To conclude the thesis considers what it would take for the ICJ to develop a biocentric legal doctrine.