This article analyses the aspect of the Court’s reasoning in Opinion 1/17 that focuses on the regulatory autonomy of the Parties to the Comprehensive Economic and Trade Agreement (CETA) to decide on levels of protection of public interests. The European Court of Justice’s (ECJ) introduction of regulatory autonomy under EU law coincides with the wider debate around ‘regulatory chill’ under international investment law. This article finds the ECJ’s concept of regulatory autonomy to be narrower than that of the regulatory chill hypothesis put forward by critics of investor-state dispute settlement (ISDS). It further analyses the ECJ’s reasoning that the CETA’s investment tribunals do not have jurisdiction to call into question the levels of protection sought by the EU. In so doing, it will critically evaluate the certainty of the ECJ’s promise that there will be no negative effect on public interest decision-making through CETA’s investment chapter. Finally, it will explore the legal consequences of Opinion 1/17 for future awards and investment agreements.