The present article focuses on the issue of possible direct application of the first pillar of the Aarhus Convention. It first points out the status of the Aarhus Convention as a so-called external agreement, which is both a source of international law and the law of the European Union, then deals with the particular criteria that must be met for an international treaty to have direct effect in the law of the European Union. Subsequently, the author applies these criteria to the Aarhus Convention, taking account of the existing judicature of the Court of Justice of the European Union within its third pillar. He goes on to test the individual norms under its first pillar and finds out whether they could have this feature. Finally, regarding the first pillar of this Convention, he addresses when its direct effect could apply in the case of the simultaneous existence of secondary European Union law in this area and what the consequences are for application practice in the Czech Republic.