This article endeavours to assess whether the Investor-State Dispute Settlement (‘ISDS’) mechanism established under the Comprehensive Economic and Trade Agreement (‘CETA’) may in fact undermine the external autonomy of the EU legal order, arguing that in Opinion 1/17 the Court of Justice of the European Union (‘CJEU’) has lowered the bar in its analysis of compatibility with this principle. After a brief overview of the notion of external autonomy the article turns to an analysis of the CETA Opinion, arguing that the CJEU confined itself to a formal scrutiny of the relevant textual provisions and failed to thoroughly explore the impact that CETA’s ISDS mechanism is liable to have in practice. The article then deploys two hypothetical scenarios, both involving the field of EU risk regulation. These will show how CETA Tribunals might indirectly interpret EU law as a matter of law and how, when assessing whether an EU measure breaches CETA, they might encroach on the EU determination of the adequate level of protection of public interests. Against this backdrop, the article argues that CETA’s ISDS system is liable to undermine the uniform and consistent interpretation and application of EU law. Further, CETA Tribunals might de facto bind the CJEU in its interpretation of EU law and influence other EU institutions in the exercise of their powers.