In the European Union (EU), environmental regulations suffer from the higher rate of non- compliance than any other sector. And yet, the understanding of what factors and conditions facilitate or impede compliance and how these factors shape variation in compliance across regulations and issue areas, is still not quite sufficient. Another feature of environmental governance concerns the growing importance of the role of informal/non-state actors, such as the non-governmental organizations (NGOs), industry actors, and the public. This research set out to uncover how environmental NGOs, as well as industry and business actors interact with the EU institutions and the domestic institutions, administration and legislature, to affect domestic environmental compliance with the EU directives. The role of public participation is also explored. Using the case of the Environmental Impact Assessment (EIA) directive in Latvia and Belgium, this research investigates the effects of these actors upon the environmental compliance in the EU; how these effects vary across compliance stages; and what domestic member-state factors account for these effects.