The Federal Constitutional Court has repeatedly ruled that a tax provision that cannot be uniformly enforced due to its legal design is unlawful because it violates Article 3, Paragraph 1 of the Basic Law. However, this purely constitutional assessment cannot be directly applied to tax law determined by European law. Therefore, the author examines how the perspective of the Federal Constitutional Court must be modified for the value-added tax law shaped by European law. In this context, a distinction is made as to whether the structural enforcement deficit lies at the level of European secondary law or is only caused by inadequate implementation by the national legislator. Special attention is given in the investigation to how individuals burdened by a structurally deficient tax provision can obtain effective legal protection.