Chapter I: Introduction: treaties in international relations
It has been claimed quite often that customary international law, that is, unwritten rules based on practice and done in the belief in their righteousness or lawfulness, is the oldest source of international law. In other words, that customary law pre-existed treaties. Logical analysis may seem to suggest the same temporal priority: a treaty can seemingly be adopted under the law only if there are some common rules on the meeting of wills, on the binding nature of the compact, and so on. However, historical analysis tends to show that treaties between relatively independent political collectivities preceded customary rules. In order to create common customary rules an ‘international society’ must have developed and some minimum sense of commonalities between the constituent collectivities must have crystallized. This was not the case in the most remote times, when each society was closed to the outside and rather bellicose in its outlook. The first limited contacts between peoples bear the hallmark of scattered agreements, such as armistices, exchange of prisoner agreements, particular alliances, and so on. Treaty law seems at the root of incipient international society. The foregoing explanations have as a logical corollary that agreements between relatively independent public collectivities are initially not rooted in a common legal order (public international law), superior to the contracting parties and providing for rules such as pacta sunt servanda. Initially, treaties are unilateral acts assumed by each contracting party under its own municipal legal order.