In this insightful book, Katherine Reece Thomas explores the constantly evolving nature of state immunity, providing a nuanced analysis of the tension between private and public law. The current rules on the commercial activity exception to state immunity are examined, in both international and domestic law settings, using recent case studies from key jurisdictions including the UK and the US. Questioning when a state can be sued in a domestic court if it engages in commercial activities, Reece Thomas reveals how a restrictive rather than an absolute doctrine has been adopted and explores the ways in which states allow commercial activity to override state immunity. The implications of this, and of how commercial activity can therefore be defined, are explored through the contexts not only of corporate law but also of central bank sanctions, human rights, employment, and crime, using recent examples from Afghanistan as well as Russia’s invasion of Ukraine. Further questions regarding immunity are posed by a crucial discussion on enforcement against state assets. Comprehensive yet concise, this authoritative work includes consideration of a range of contexts and implications for the commercial activity exception. It provides a valuable resource for students, researchers and practitioners in international commercial law and public international law, as well as in international relations.