The principle of the federal state is one of the unchangeable constants of the German Basic Law. This makes it necessary to ascertain the content of the so-called "statehood" of the federal states (the "Lander") with respect to the central state. Also, the European integration, gearing towards continuous change, repeatedly calls for re-measurements and re-evaluations of the guarantee of the federal principle. Ines Gillich develops a conceptual framework to break down the elements of statehood of the "Lander" and examines whether this concept is preserved or relativized in the process of European integration.