In the international legal literature, it is commonplace to talk about the law of state responsibility as secondary rules of law. The terminology emphasises that in some way or another the law of state responsibility is different from other rules of the international legal system – what international legal scholars refer to as primary rules of law. The present essay inquires into the soundness of this language. As argued, the primary-secondary rules terminology builds on two assumptions. First, it assumes that the law of state responsibility can be described as separate from the ordinary (or primary) rules of international law. Secondly, it assumes that the two classes of rules can be described as pertaining to different stages of the judicial decision-making process. As shown in this essay, neither assumption can be defended as correct.