The fundamental elements of the international legal system remain subject to debate. Constitutionalism is merely the latest instalment of this continuing conversation on the very nature of international law. In this context certain foundational aspects may be labelled as the system’s ‘constitutional processes’. The primary argument presented in this article is that principles and ‘general principles of law’, two frequently overlooked categories of norms, are particularly useful tools for the enhancement of these constitutional processes. While often conflated, principles and general principles are distinct, performing different roles in the architecture of the international legal system. Renewed attention and debate on the norms beyond treaties and custom is critical for the enhancement of international law’s systemic features. Two broad examples are given in support of this claim. First, general principles of law have the potential to add substance to the notion of an international community and the role of this community in the creation of international norms. Second, the legal framework for the judicial settlement of international disputes can be rendered more robust through the use of principles and general principles of law. While attempting to redesign or reconceptualise the system, constitutionalists have failed to actually engage with the system. Yet, the popularity of the constitutionalism debate presents an opportunity to re-examine the system’s constituent norms and consider their potential to strengthen international law’s constitutional processes.