This book investigates how state responsibility can be determined for the wrongdoing of non-state actors. Every day, people, businesses and societies around the world pay a price arising from interactions between states and non-state actors. From insurrections that attempt to create new governments, to states arming belligerent proxies operating overseas, to companies damaging natural environments or providing suspect services, the impact of such situations are felt in numerous ways. They also raise many questions relating to responsibility. In answering these, State Responsibility for Non-State Actors provides a picture of what the law governing this area is, what it could be, and what it should be in light of past histories, present realities and future prospects.