Chapter 1 of Part I assesses the extent to which scholars and analysts of IL provide compelling explanations for distinctive American IL policy. An increasing number of analyses have drawn on the pedigree of a long-established literature on ‘American exceptionalism’. As a term of art in political science, American exceptionalism refers to the idea that history and values set the country qualitatively apart from other nations, which is the meaning followed in this book as the most historically grounded and analytically useful. In contrast, increasing use in legal scholarship has more often narrowed the concept to pejorative shorthand for the American practice of seeking ‘exceptions’ to global legal rules, and therefore as uniformly detracting from the international rule of law. This chapter unpacks these accounts by focusing on three common explanations for idiosyncratic policy: the expected rational behaviour of a state with uniquely preponderant global power; distinctive American jurisprudence; and unique political culture forged in the nation’s historical experiences. Read together, these three explanations exhibit striking correlation, indicating the need for a fresh account that maps deep-seated connections between the ideas and interests shaping IL policy.