Ideas and practices often perceived as modern carry a complex premodern history that cannot be excised from their present. This is certainly the case of trade embargoes as economic means for the attainment of political goals. For a variety of reasons, however, tracing change over long periods of time remains an exercise in chronological and spatial jurisdiction. Further complicating our understanding of the convoluted relationship between past and present has been the increasingly pronounced tendency to write in the vein either of a “history of ideology” or, conversely, of a “history of action.” In fact, “theory” and “practice” existed in a dialectical relationship, a cyclical tug of war that produced not so much winners and losers as complex realities that require a thick reading of legal, political, cultural, and social change. This chapter, by contrast, seeks to explain the transfiguration of the legal tradition from the perspective of international law history by focusing on two interrelated transitions.