Jacco Bomhoff is principally concerned with the character of constitutionally salient boundaries. In its first part, this chapter explores the contrast between, on the one hand, recognition of the legally mediated character of borders and jurisdictional boundaries in critical scholarship, and, on the other hand, unquestioning determinations of ‘inside’ and ‘outside’ in judicial practice. The second part of this chapter, then, approaches the question of the character and effects of constitutional boundaries by way of a case study on mobility. Mobility, in its many different forms – its restriction and its excesses, for individuals and for corporations – lies at the heart of many pressing contemporary challenges. The legal treatment of mobility, however, is fragmented across many different specialised fields – from immigration law, to tax law, to international arbitration – in which constitutionalist concerns are rarely central. The chapter aims to address this lacuna by sketching the contours of an ‘outward-facing constitutionalism’ which could provide the conceptual and normative means to scrutinise the constitutional implications of the regulation of ‘access’ and ‘exit’ for both individuals and corporate actors.