This paper engages two different discourses of the good life[2] in conversation: what Beitz calls 'the classical theory of sovereignty', and green political theory.[3] Both have been concerned with questions as to how to realise the good life, but have recognised different obstacles to that end, and have taken relatively little notice of one another's insights and inquiries. This neglect has had the consequence of impoverishing green conceptions of the institutional arrangements required to deliver environmental sustainability, a necessary if not sufficient condition of the green good life. Likewise, classical theorists of sovereignty have been remiss in their failure to recognise the need to enlarge their understanding of threats to human security by including environmental concerns.