To what extent do constitutional basic rights limit the legislator in the field of substantive criminal law? This is the main question of this article. Its dilemma is that, at least from a continental view, we have two 'disciplines' dealing with them: constitutional law and criminal law. The divergence culminates in the concept of the Rechtsgut (public value or interest), which serves as a starting point in the criminal law arena. This difference was decisive in a case where the German Constitutional Court stated that the punishment of incest between natural siblings is not contrary to the German Basic Law. Criminal lawyers disagree with that ruling because the criminal law provision does not protect a legitimate Rechtsgut. The 'criminal law school' of the Rechtsgut puts all aspects of legitimate ariminalization into one and only box: 'the' Rechtsgut. This is not convincing from the point of view of constitutional law.