This study examines to what extend the right to access environmental information that is enshrined in the Aarhus Convention, the Environmental Information Directive and national law can be used by the public to access information related to compliance with EU environmental law with a view to identifying non-compliance. The study looks at the EU Emissions Trading System as an example of EU environmental law and applies a threefold methodology, doctrinal, comparative and empirical in order to determine whether information that is necessary to identify non-compliance must be available upon request and is made available in practice.