The Court of Justice of the European Union's recent tendency to give environmental associations more rights to obtain information and appeal in court suffered a setback in 2015. As the European Union (EU) is a contracting party to numerous bilateral and multilateral international treaties, it is bound by the Aarhus Convention (AC). It is an actor in the international community, which shapes the international system and has impacts on its internal legal order. When the EU ratified the AC in 2005 it committed to guaranteeing broad access to justice in environmental matters at both national and EU levels. The chapter debates whether EU secondary legislation like the Aarhus Regulation and EU institutions' decisions may be reviewed against criteria of international treaties such as the AC. Review of EU secondary law and EU Acts against the standards of international agreements has lately become the exception rather than the rule, which might lead to even less engagement of the EU legal order with international law and therefore weakened influence for international environmental law. To understand this contentious jurisdiction it is crucial to understand the relationship between international and EU secondary law. Relevant case law is illustrated and possible reasons for the different outcomes are discussed.