Among the features of emerging decision-making structures, the participation of non-governmental organisations (NGOs) may be the least amenable to traditional models of world politics. For political leaders and scholars alike, NGOs' place and legitimacy as independent global actors remains contested. International environmental law making has presented a useful vehicle for the study of NGOs and civil society in this new global context. Along with human rights, international environmental law stands at the forefront of international law making. A relatively new area of intensive international regulation, its institutional features are thus only now being mapped out, and can reflect the evolving role of NGOs in a way that more entrenched regimes cannot. This article examines major theoretical approaches to NGO participation in international law, both generally and with specific application to international environmental law. It also considers their place in liberal theory, focusing on NGOs as stakeholders acting through international institutions and as freelancers acting through the marketplace.