This chapter serves as the introduction to an edited collection of original essays first presented at an international conference at the Transnational Law Institute, King’s College London. The conference had as its focus the commemoration of the 60th anniversary of the publication of Philip Jessup’s landmark study, “Transnational Law”, published in 1956. Jessup’s slim book is often associated with having launched an investigation into the role that law can play in the context of border-crossing human and institutional relations. Whatever the relationship between cause and effect, such an investigation is still continuing. But, the context in which Jessup wrote – as an international lawyer, an arbitrator and economic lawyer – is a different one today. And, that is true also for the disciplines that have taken an active interest in what is and isn’t transnational law. The chapter places Jessup’s main findings into a context of global geopolitical change and domestic state transformation. Both render the interdisciplinary investigation into law’s role in a global context ever more crucial. That “transnational law” – as label, concept or methodology – occupies an important place in this undertaking should be seen less as a marker of a new, self-standing doctrinal legal field, than as an important opportunity to think about the foundations of law today in a volatile, deeply divided world. This forms the backdrop for transnational law as a methodological laboratory in which to study law’s relation to other forms of social ordering, its sources and norms, its actors and processes, its regulatory aspirations and democratic (and, other) infrastructures.