I argue that in some circumstances the capacity for voluntary agreement making can be an adequate realization of the All-Affected principle. The basic idea is that one can, with this capacity, attempt to advance one’s interests by entering into voluntary agreements with others. The All-Affected Principle can be satisfied if persons are able to enter into agreements with those whose actions affect them or with those who can advance their interests. Persons should have an equal say or a say proportionate to their legitimate interests and this can be realized in voluntary agreement making, or so I shall argue. I draw an analogy between democratic decision making traditionally conceived and voluntary agreement making. This helps us see how we can define appropriate procedural norms for the evaluation of processes of voluntary agreement making in both market and international contexts. I argue that fair voluntary agreement in markets and international decision-making is a realization of the same principle as fair collective decision-making in democracy only one is for decentralized decision making and the other is for centralized decision making.