In this talk, I analyze the legitimacy of this canon from a constitutional theory perspective by highlighting normative questions that the employ of this canon raises regarding the role of the judiciary when enforcing the constitution. I trace this canon back to its German origins, compare it to the US avoidance canon, and elaborate on four conditions for its use. I then discuss three arguments that can be made in support of this canon. Next, I examine the principal objections that have been raised against this canon. I then intend to dispel these objections by arguing for a broad concept of legal argumentation in combination with my theory of practical institutional concordance. I argue that by balancing the competences of the state authorities involved the conditions and limits of constitutionally conforming interpretation can be reconstructed. I conclude that constitutionally conforming interpretation is a legitimate canon of generic constitutional law.