This article aims to assess the eff ectiveness of two systems of governance with respect to the making of international treaties: the Canadian system, where the decision-making process is more centralized and where intergovernmental mechanisms are poorly institutionalized; and the Belgian system, where substate actors have the role of co-decision and where intergovernmental mechanisms are highly institutionalized. The central question to be discussed is: is the fact that one gives an important role to sub-state actors in the making of a country’s treaty by means of institutionalized intergovernmental mechanisms something that negatively or positively aff ects the foreign policy of a state? And is this a positive- or a negative-sum game at the level of the conclusion and implementation of treaties? Th e article concludes that the Belgian system is more eff ective, largely because its sub-state actors have an important role at every step of the conclusion of a treaty.
