Is it important to conceptualize transnational law and “map” it as a new legal field? This article suggests that to do so might help both juristic practice and sociolegal scholarship in organizing, linking, and comparing disparate but increasingly significant types of regulation. To explore the idea of transnational law is to raise basic questions about the nature of both “law” and “society” (taken as the realm law regulates). This involves radically rethinking relationships between the public and the private, between law and state, and between different sources of law and legal authority. Taking as its focus Von Daniels's The Concept of Law from a Transnational Perspective and Calliess and Zumbansen's Rough Consensus and Running Code (both 2010), the article considers what approaches may be most productive, and what key issues need to be addressed, to make sense of broad trends in law's extension beyond the boundaries of nation-states.