This ZSE Special Issue is in honour of Joachim Jens Hesse, a scholar whose multi-faceted work may be characterised as an attempt at “crossing border” in several respects. These primarily include fostering interdisciplinary cooperation between law, economics and social sciences, analysing public sector developments in an international and intercultural perspective as well as bridging the “gap” between academia and practical politics. Therefore, the volume deals with a subject that covers these features in an exemplary manner: the interrelationship between nation-state constitutions and their international environments. In this context, ongoing processes of transnationalisation have not only contributed to blurring the formerly clear-cut boundaries between these two domains, but also provoked a growing interest in and demand for comparative, interdisciplinary and applied research on constitutional developments. The present contribution highlights the “cross-border” aspects of Hesse's work, points to some theoretical and analytical challenges of the topic and provides an outline of this Special Issue.