The increasing role that NGOs play at different levels of legal relevance - from treaty-making to rule implementation, and from support to judges to aid delivery - calls for reconsideration of the international legal status of those organizations. This book shows that the degree of flexibility currently enjoyed by NGOs in fields as varied as human rights, the environment and the European Union development cooperation policy constitutes the best arena for all actors involved, with the consequences that the instances where more strict regulation of NGOs' participation is desirable are very limited.