The rational choice analysis in this chapter focuses on exemptions of certain types of conduct from state responsibility. It analyses how the six different circumstances precluding wrongfulness in international law integrate the protection of community interests in their incentive structures regarding the plaintiff state alleging the breach of an international obligation or the defendant state invoking a justification or excuse. What all defences have in common is that they allow for flexibility in exceptional circumstances and thus for non-compliance with the international obligation in question, while trying to avoid abusive invocation by setting relatively strict conditions for invocation. The key issue in this chapter is not only the allocation of duties, thus the conditions for invoking the different defences, but foremost the question of cost allocation following such invocation, thus their financial consequences. This issue had deliberatively been left open in the ARSIWA. Whether compensation is economically justified depends on the underlying economic rationale of each circumstance precluding wrongfulness (i.e. necessity, distress, force majeure, consent, self-defence, and countermeasures). For instance, regarding the necessity excuse, this chapter suggests differentiating between situations in which the defendant state protects an essential state interest (private necessity) or a prevailing community interest (public necessity).