Any legal system, including the international legal system, consists of rules that serve multiple purposes and functions that the legal system in question needs to perform in order to survive as a viable organism. Jurisprudence of national and international courts relating to areas such as responsibility, immunity, and dispute settlement has involved intensive discussions as to the nature and implications of the various categories of rules. Approaching this broad area, with its multiple components, requires careful differentiation of the nature of those various categories of rules, for the fact that the relevant classification of rules works in one area does not inherently make it workable in other areas, which is confirmed in practice. The most problematic issue remains the judicial application of jus cogens in relation to state immunities and the ensuing distinction between substantive and procedural rules. It is shown in this contribution that this artificial distinction does not reflect the functions international law actually accords to its various rules, and is instead a product of political and ideological preference to keep particular classes of plaintiffs out of certain jurisdictions.