The emergence of global environmental responsibility as a fundamental norm, or primary institution, in International Relations represents a dramatic expansion of the normative horizon of international society. The successful norm transfer from world society to international society was made possible by a transnational alliance of environmentalists and scientists, as well as representatives of states and international organisations, which acted as norm entrepreneurs to inject environmental ideas into the international agenda. In the end, its successful establishment in international society depended on it being championed by powerful states, which exported domestic environmental norms to the international level. As such, the greening of international relations represents a complex process of political enmeshment between international and world society, but it has done relatively little to slow down global environmental degradation. The norm of global environmental stewardship is still honoured more in the breach than in the observance.