Abstract The Australian debate over Investor-State Dispute Settlement (ISDS) sharpened in 2023 because Australian mining billionaire Clive Palmer, having previously registered his mining company in Singapore, has claimed to be a Singaporean investor. He is using ISDS provisions in the 2012 ASEAN-Australia-New Zealand Free Trade Agreement and the amended 2017 Singapore-Australia Free Trade Agreement to sue the Australian government for a total of A$410 billion in three separate claims. This article uses Cox’s critical theory framework developed by Schneiderman to explain the historical development and power dynamics of ISDS, the contest between its business supporters and social movement critics, and the impact of this contest on governments. It then analyses the Palmer claims and explores the global debate about ISDS, including its increased use by fossil fuel companies against government regulation of carbon emissions, which has led to increased resistance from social movements and governments. ISDS is also being reviewed by the United Nations and World Bank institutions which provide arbitrators for its tribunals and by the Organisation for Economic Co-operation and Development. The conclusion assesses the debate over whether ISDS can be reformed and its future viability.