The protection of the global environment has become one of the central objectives of the international community in recent decades. Issues such as climate change, the depletion of the ozone layer, and the loss of the biological diversity has resulted in a growing international awareness of the problems facing the planet. Moreover, there is also recognition that States will need to act more collaboratively at the international level if effective solutions are to be found to these problems. However, concurrently there is also recognition that many States have pressing socio-economic concerns of their own, and that they have neither the resources nor the capabilities with which to devote to such global issues—so called “developing” States. This article examines the response of international environmental law to these two, potentially opposing, trends, viz., the need for universalism, on the one hand, and sensitivity to the needs of developing States, on the other. In particular, the article will examine the emerging legal principle of “common but differentiated responsibilities”, as well as discussing the various means of operationalising it. Nevertheless, as will be discussed below, there is still much debate as to the conceptual basis of this principle—leading one to question its real aim. Is it to contribute to a fairer world system in which developed States recognise their historical responsibility for past environmental damage, or is it simply an expedient means of ensuring the participation of developing States in what are primarily Northern concerns?