International criminal law ("ICL") is legally plural, not a single unified body of norms. As a whole, trials for international crimes involve a complex dance between international and domestic criminal law, the specificities of which vary markedly from one forum to the next. To date, many excellent scholars have suggested that the resulting doctrinal diversity in ICL should be tolerated and managed under the banner of Legal Pluralism. To our minds, these scholars omit a piece of the puzzle * This version of the article is longer than the shorter version we have published with the American Journal of Comparative Law. This longer version includes a fourth part focused on criminal law procedure. In this additional part, we set out the eclectic nature of Argentine criminal procedure as a null hypothesis, since it shows evidence of a congruence between criminal law doctrine and surrounding social values that acts as an exception to the trend we identify in our other examples. We then qualify this Argentine counterexample by discussing the history of employing divergent criminal procedure in post-WWI trials to show instances when ICL must adopt a unified standard for functional reasons. In this longer version, we also weave the insights from these two examples of criminal procedure throughout the remainder of the piece.