Two of the most important forebears of IR as a discipline were international law and diplomatic history. International law, as an organic element of the state system, is likely to be important as long as the state system functions. Indeed, it may outlast that system by becoming the legal component of various world society approaches or transnational regimes. Moreover, international law can be seen in many guises. 1 For example, the notion that law is the sovereign’s command and is only law so long as it is backed by an effective sanction fits well into the realists’ schema. Moreover, the historical derivation of international law must not be forgotten: it arose out of the Christian Commonwealth of Europe and was imposed by the rising European Powers on the rest of the world, whether they liked it or not. It reflected European values of Christianity and capitalism – the prevailing social and economic system – and it became a world system through colonialism and, where necessary, through coercion.