The two starting points for this chapter are that fields of law are inventions, and that fields matter as analytical frames. All legal systems deal with foreign relations issues, but few have a field of “foreign relations law.” As the best-stocked cabinet of issues and ideas, U.S. foreign relations law would be likely to generate the field elsewhere in the process of comparison. But some scholars, particularly outside the United States, see the nationalist or sovereigntist strains of the U.S. field, and perhaps even just its use as a template, as demoting international law. The chapter begins by asking whether this apprehension can be alleviated by using international law or an existing comparative law field to inventory the foreign relations issues to be compared. Finding neither sufficient, it turns to the U.S. field as an initial frame and sketches three types of anxieties that the U.S. experience has raised or might raise for international law. The chapter concludes by suggesting how Campbell McLachlan’s allocative conception of foreign relations law might be adapted so as to turn such anxieties about international law into opportunities.