Unhealthy diets are a leading cause of death and disability globally. The WHO recommends Member States implement front-of-pack (FOP) nutrition labels to guide consumers towards healthier food choices, as part of comprehensive strategies to prevent diet-related non-communicable diseases. Interest in FOP nutrition labelling is increasing, but there is limited guidance for policymakers developing regulations necessary for effective implementation. A rapidly evolving evidence base, limited regulatory capacity and possibility of legal challenge by affected food industry stakeholders can create ‘regulatory chill’, whereby governments are dissuaded from progressive public health policymaking. We use a framework for analysing public health law and available best-practice guidance to evaluate key components of 31 FOP nutrition labelling regulations endorsed by governments up to June 2019. Analysis of regulatory form shows recent rapid uptake of label formats that are easier for consumers to understand and increasing use of mandatory legislation. However, policymakers must decide much more than whether to apply ‘stars’, ‘traffic lights’ or ‘stop signs’. The substance of effective regulation must contain strategic regulatory objectives, clear specifications for displaying the label on pack, a valid scoring mechanism and a justified scope for including foods. While there are limited data on current practice, good governance of FOP nutrition labelling regulation also requires transparency and accountability in processes of label development, implementation, evaluation and enforcement to promote continuous improvement and withstand undue commercial interference. Whether developing new FOP nutrition labels or reforming existing ones, our findings support policymakers to design and implement best-practice, evidence-informed regulation.