The effectiveness of a state's claim to territory has long been one of international law's central concerns when determining territorial entitlement. However the concept has always been the subject of controversy, as states and empires have adapted the notion over the centuries to suit their acquisitive ambitions, sometimes using it to challenge their rivals' exorbitant territorial pretensions, and other times invoking it to validate their own seizure of territory by unlawful means. In the last century, as the international legal system has undergone profound changes in its structure and...