This book offers insights into how international investment law (IIL) has frustrated states' protection of human rights in Latin America, and IIL has generally abstained from dealing with inter-regime frictions. In these circumstances, this study not only argues that IIL should be an object of contention and debate ('politicisation'). It also contends that Latin American countries have traditionally been the frontrunners in the politicisation of international legal instruments protecting foreign investment, questioning whether the paradigms informing their claims' articulation are adequate to frame this debate. It demonstrates that the so-called 'right to regulate' is the paradigm now prevalently used to challenge IIL, but that it is inadequate from a human rights perspective. Hence, the book calls for a re-politicisation of IIL in Latin America through a re-conceptualization of how states' regulation of foreign investment is understood under international human rights law, which entails viewing it as an international duty. After determining what the 'duty to regulate' constitutes in relation to the right to water and indigenous peoples' right to lands based on human rights doctrine, the book analyses the extent to which Latin American countries are currently re-politicising IIL through an articulation of this international duty, and arbitral tribunals' responses to their argumentative strategies. Based on these findings, the book not only proposes investment treaties' reform to anchor the 'duty to regulate' paradigm in IIL, and in the process, to induce tribunals' engagement with human rights arguments when they come to underpin respondent states' defences in investor-state dispute settlement (ISDS). In addition, drawing upon the (now likely defunct) idea of creating a regional ISDS tribunal, the book briefly reflects on options available to such a tribunal in terms of dealing with troubling normative/institutional interactions between regimes during ISDS proceedings.