The conference deals with the connection between the law of treaties and the law of international responsibility. Following the Rainbow Warrior award and the GabÄíkovo-Nagymaros judgment, it is now commonplace to think of the law of treaties and the law of international responsibility as being in a relationship of 'functional separation'. The law of treaties relates to so-called 'primary rules', while the law of international responsibility is a set of 'secondary rules.' But scratching beneath the surface, problems and uncertainties begin to emerge. Is the functional separation between the law of treaties and the law of responsibility airtight or is it porous, and does this matter? For instance, is the suspension of the performance of a treaty obligation by way of countermeasures in essence the same as the suspension of the treaty itself; can the formal distinction be maintained and, if so, to what end? Further, to what extent do treaties containing specific provisions on 'secondary rules' exclude the application the general rules of international responsibility? And what role does the law of responsibility have (if any) in respect of treaties which set up their own 'compliance mechanisms'? Or if a State enters into an international agreement with a non-State actor and either party breaches the agreement? Or if a State fails to comply with a treaty which is only being provisionally applied?