General Introduction

The international activities of subnational governments (SNGs) have become a subject of increasing scholarly interest across various disciplines, including international relations, political science, legal studies, and urban studies 1 ( Tavares, 2016 ; Aldecoa & Keating, 2013 ; Soldatos, 1990 ). This growing scholarly and policy interest stems from the fact that the international engagements of SNGs go against the grain of the traditional Westphalian model of international relations, which conventionally puts foreign policy and diplomacy within the remit of central governments in sovereign nation-states ( Bernier, 1973 ; Hayes, 2004 ). The pre-eminence that sovereign states enjoy in this regard is also evident in the state-centric bias of traditional theories of international relations, international law, foreign policy, and diplomacy.