The principle of subsidiarity was incorporated into the Maastricht Treaty and was sanctioned as a regulation of the exercise of competencies. In its European legal form, it reflects back on German constitutional law. The Basic Law explicitly recognizes it in its new structural safeguard clause as one of the guidelines for national integration policy, which should follow German constitutional patterns. The principle of subsidiarity is part of the image that the Basic Law portrays of itself. Today, as the text on the principle of subsidiarity is published in its second edition, the topic is once again on the agenda of jurisprudence. The old questions regarding content and meaning, applicability and justiciability arise again, now not only in the context of national law but also in that of supranational law. Well-known controversies regarding the validity of statements.