Within the coming decade, the deployment of artificial intelligence (‘AI’) appears likely to have a disruptive impact on global affairs. What will such ‘globally disruptive’ AI imply for the form, function and viability of international law? I briefly sketch the long history of technological innovation driving, shaping and destroying international law. Drawing on scholarship on the relation between new technologies and international law, I argue that new technology changes legal situations both directly, by creating new entities or enabling new behaviour, and indirectly, by shifting incentives or values. I argue that development of increasingly more disruptive AI may produce three types of global legal impacts. The first is ‘legal development’ (patching); the second is ‘legal displacement’ (substitution); the third is ‘legal destruction’ (erosion). I discuss the potential impact of AI in all three modalities, and the implications for international relations. I argue that many of the challenges raised by AI could in principle be accommodated in the international law system through legal development, and that while AI may aid in compliance enforcement, the prospects for legal displacement - a shift towards an ‘automated international law’ - look slim. However, I also conclude that technical and political features of the technology will in practice render AI destructive to key areas of international law: the legal gaps it creates will be hard to patch, and the strategic capabilities it offers chip away at the rationales for powerful states to engage fully in, or comply with, international law regimes. This suggests some risk of obsolescence of distinct international law regimes.