This book offers a foundational rethinking of how international law engages with non-state effective territorial entities - territories that, while legally part of a state, are de facto governed by non-state actors or other states.

These entities - ranging from ISIL-controlled areas in Syria to Taiwan - occupy an increasingly prominent place in global politics, yet their capacity (and thus, responsibility) remain inadequately theorised in general public international law doctrine. Rather than assessing these territories through the binary lens of statehood, the book begins by assuming their non-state status and asks: what legal capacity and responsibility do such entities hold under international law?

Shunning the confines of theory, the book studies practical problems in four examples from across the spectrum of the state-like: ISIL in Syria, Crimea, Somaliland, and Taiwan. The book also moves beyond isolated analyses of conflict or self-determination to offer a more holistic and pragmatic account of what these entities reveal about the limits and possibilities of the current international legal framework, and explores the broader implications for concepts like sovereignty, territorial integrity, and recognition. It argues for a more functional understanding of legal capacity and responsibility that acknowledges the realities of territorial control without forgoing the notion of statehood.

Combining doctrinal clarity with pragmatic ambition, this book challenges the state-centric foundations of international law and offers a roadmap for engaging with one of its most pressing contemporary challenges: the legal accommodation of non-state territorial authority in a world still structured around states.