International economic law imposes limits on policy spaces. But scholars rarely study empirically the interpretive acts that determine the accepted meaning of investment or trade law as applied to a specific regulation long before a formal dispute. To fill this gap, we focus on interpretive contests over the meaning of WTO law between corporations and bureaucrats and their implications for states’ policy space. Based on a case study of Chile’s landmark 2015 nutrition labeling regulation and drawing on documents from freedom-of-information requests as well as interviews, we make two arguments. First, superior resources and a favorable global institutional environment enable transnational corporations to directly assert self-interested interpretations of international law to social regulators worldwide. Second, national bureaucrats can only refute these business-friendly interpretations and claim policy space by drawing on relevant expertise, in-house or through inter-agency cooperation.