In the short history of the US bilateral investment treaty (BIT) programme, there have been no instances of dispute settlement cases initiated against the United States by firms from BIT countries. The NAFTA experience changed that. Where other studies have only hinted at the reasons for NAFTA controversies, this paper makes clear three causal factors: (i) changing patterns and intensity of FDI, (ii) the application of those rules to developed countries amid those changing FDI patterns and (iii) ambiguities in ISDS rules themselves. The paper explores these and traces the ways in which lessons of the NAFTA have been instrumental in changing the pursuit of investment protection agreements. BITs used to be uncontroversial, but the NAFTA focused attention on reforms to ISDS that maintain the utility of BITs in the governance of FDI, without creating a legal structure for simply challenging the state.