The current international system is based on Westphalian principles in which authority is defined territorially, within which the state has sole jurisdiction. Adherence to these principles has contributed to the decline of interstate war, but, for states that gained independence after 1945, it has contributed to civil conflicts. The norms are opaque and provide poor guidelines as to when, and on which grounds, external intervention in civil wars might be warranted. Hendrik Spruyt argues that the degree to which the combatants challenge Westphalian principles should guide policy responses. Furthermore, the international legal regime should reconsider partition as a potential solution to civil wars.