This article takes as its starting point the failure of the so-called normative wing of the English School to theorise the foundational determinants of value from which international society derives its normative character. In other words, they have not adequately thought through ‘the law behind the law’; that is, the underlying basis of obligation in international life. Thus, English School theorists are able to describe and to explain various norms but they cannot make sense of the reasons why any of these norms should be regarded as obligatory. Failure in this regard is attributable in large part to the way in which pluralist and solidarist conceptions of international life are typically understood as representing conflicting moral claims. This article seeks to move beyond these seemingly incommensurable claims, and the debate to which they give their names, by putting forward an account of obligation that reconciles the unity of human community and the freedom of international society in a single, intellectually coherent argument. The article concludes by arguing that a normative version of English School theory formulated in this way opens space for thinking through much of what still confounds the English School, including the normative character of political economy, the existence of a rational order of values, and the ever elusive meaning of world society.