The Introduction unfolds the book’s central claim that the very meaning of commitments to ‘the international rule of law’ is informed by long-established and competing foreign policy ideologies. These ideologies continue to structure profoundly contested meanings as between American policymakers and their global counterparts, and between American policymakers themselves. The book’s guiding question is thus: what does the ‘international rule of law’ mean for American legal policymakers even as they advocate competing commitments to international legal order? The chapter sets out the framework for exploring ideology in IL by mapping out the nature of interdisciplinary research between IL and the IR subfield of FPA. The book’s object of analysis in American ‘IL policy’ is introduced, which is an original concept capturing the specific form of foreign policy concerned with conception of and strategies taken in relation to international legal rules and institutions. The chapter concludes with a brief history of US engagement with international criminal courts and the ICC specifically, which stands out as the leading demonstration of competing conceptions of the international rule of law as they influence global legal order.