This research project offers a novel contribution to the measurement of the effectiveness of Regional Organisations (ROs). First, it creates a methodological framework for the analysis of citizen participation. It then conducts in-depth qualitative research on the implementation of citizen participation in two ROs. Lastly, two indexes of citizen participation are built, one related to its regulation and the other to its implementation: the indexes of de jure and de facto citizen participation. Finally, these indexes are used as explanatory variables in a structural gravity model for international trade, advancing economic studies on the evaluation of RO treaties.