This chapter looks, inter alia, at how international law has been used or could be used to help tackle the most significant environmental challenge of our time. This challenge is global climate change. Not many topics provide a good illustration of the importance of a globally inclusive regulatory regime focused on preventive and precautionary approaches to environmental harm—or of the problems of negotiating one on such a complex subject. Solutions to global climate change have not been easily forthcoming. The chapter looks at the efforts of the international regulatory regime to address these challenges by recourse to novel ‘market based’ mechanisms and differential treatment. An example is the post-Kyoto scheme for reducing greenhouse gas emissions through ‘nationally determined contributions’. In the end, the chapter argues, it is likely to be technology that enables us to grapple with the causes of climate change, not law, but law can drive technological change, as it has with ozone depletion and acid rain.