Climate change has arisen as the most pressing global challenge of our time. In the post-1989 economic consensus based on market mechanisms and eschewing command and control regulation, the concerted global response to this problem has taken the form of flexibility mechanisms harnessing the market in order to steer development in the direction of a low-carbon economy. From this perspective, the flow of foreign investment towards developing countries – and in 2012 for the first time investment flows to developing countries surpassed those between developed countries – can be one of the most effective tools to pursue an environmentally sustainable and climate-friendly economic development. The legal response to climate change, exemplified by the measures contained in the Kyoto Protocol – Clean Development Mechanism (CDM), Joint Implementation (JI) and International Emission Trading (IET) – is designed to harness foreign investment for sustainable development and emission reduction projects by providing economic incentives for the transition to a low-carbon economy. On the downside, the mechanisms, when employed within global value chains for the production of consumption goods for developed countries’ markets, can be used to offshore emissions from developed to developing and least developed countries without achieving an overall reduction in carbon emissions. As these countries do not have emission reduction targets, any failure down the chain of production in projects started under the aegis of the CDM, for example, might result in a net increase of emissions (so-called ‘carbon leakage’). The picture from within the investment regime is equally mixed. Traditionally, the investment regime has been instrumental in reducing the regulatory risk for foreign investors; in the case of environmental measures this meant protection against the ratcheting up of standards to the detriment of investors engaged in highly polluting and/or carbon intensive sectors such as mining and extractive industries. Numerous investment arbitrations have concerned environmental measures and this has been the case especially under the umbrella of the NAFTA. The rise of ‘environmental’ arbitrations has functioned as a catalyst for changes within the investment regime in the direction of its diversification, clarification and hybridisation. In fact, the latest UNCTAD Investment Report confirms the trend towards the inclusion of ‘sustainable-development-friendly provisions’ in International Investment Agreements (IIAs), via the insertion of clauses dealing with environmental, labour and human rights measures. The fact that investors might avail themselves of IIAs to protect climate-friendly investments from non-commercial regulatory risk is certainly not noteworthy per se – the ‘legitimate expectations’ doctrine and contractual stabilization clauses have been developed precisely to deal with this sort of risk – and yet, in the quest for legitimacy of the investment regime, this has been presented as another added value. From this synergic perspective, IIAs are presented as providing a further layer of protection of ‘green investors,’ against loosening/reducing of support mechanisms used to attract low-carbon investments and switching projects. This synergic potential notwithstanding, conflicts arising by regime intersection have attracted more attention. In this chapter, as in much of the available literature, the focus is on the conflicts generated within the investment regime, which, as a consequence of its sophisticated system of dispute resolution, is more likely to have to deal with them and better equipped to do so. This interaction can be read on a purely international plane, whereby climate change legal obligations, enshrined in the 1992 United Nations Framework Convention on Climate Change (UNFCCC) and its 1997 Kyoto Protocol (as amended in the 2012 Doha Amendment), conflict with the obligations contained in IIAs. International law possesses several tools, from interpretation to general rules of conflict resolution and specific conflict clauses in the applicable IIAs, to prevent or resolve these conflicts.