The global investment regime is a prime example of the so-called ‘politicization beyond the state.’ Investment agreements with an Investor–State Dispute Settlement (ISDS) mechanism have become contested in several corners of the globe, triggering a widespread reform process encompassing national, regional and multilateral levels. This article examines the consequences of this confluence of politicization processes, focusing on the European Union (EU) and two key venues of ISDS reform: the United Nations Commission on International Trade Law (UNCITRAL) and the Energy Charter Treaty (ECT). Combining different strands of politicization literature in International Relations and Political Science, the article advances a nuanced conceptualisation of the institutional consequences of politicization that goes beyond a deepening/decline dichotomy. Instead, the article examines whether and how politicization generates ‘authority shifts,’ either through a vertical move between international and national levels; and/or through a horizontal recalibration between public and private forms of governance. The article argues that although the EU’s initiative for global ISDS reform intended to rebalance public and private authority while strengthening its international character, the on-going reform processes at the UNCITRAL and the ECT may eventually lead to a (partial) dismantling of international authority.