Not only do interest groups lobby, but regions do too: This book re-examines federalism through the lenses of interest groups and lobbying research. It focuses on ‘shared rule’, a foundational pillar in federal theory that necessitates the active involvement and representation of subnational units in federal policymaking. Based on new and original data, the study illuminates how the 26 Swiss cantons make their voices heard at the federal level. It explores traditional federal institutions, such as second chambers, alongside professionalised tactics of intergovernmental lobbying. Furthermore, the book empirically analyses the conditions under which the cantons succeed in shaping federal policy and politics according to their preferences.