The main issue in this thesis is the existence of “moral concepts” – concepts pursuing altruistic rather than self-serving ends – as non-conventional law, i.e. as customary international law or general principles of law. The question will be examined in particular in the context of the doctrinal discourse in order to question the phenomenon of the too rapid observation of their existence. A series of preliminary questions relating to the UN Charter will first be set out, which will serve as a framework for discussion. Then follow the unconventional sources of international law. Finally, the essential element of international relations underlying the main question of this thesis will be discussed: the interest of the State. The latter discussion will be illustrated by examples of human rights and the use of force on humanitarian grounds. ; The main question of the thesis is whether ‘non-treaty’ law – that is customary international law and general principles of law – may exist for ‘moral concepts’ – ideas that follow an altruistic as opposed to a self-interested motivation. In particular, this possibility is discussed against the background of doctrinal discourse on the issue, in order to confront the casual assessment that this is the case. The argument is advanced in three steps. First, a row of preliminary questions under the UN-CHARTER is set out for further discussion. Second follow the “non-treaty” sources of international law. Third stands the essential element of international relations underlying the main question of this thesis: state interest. The latter discussion is complemented by two case studies, one on human rights and one on humanitarian use of force. ; Die Forschungsfrage bezieht sich auf die Existenz von „moralischen Konzepten“ – also solchen, die einer altruistischen anstelle einer eigennützigen Motivation folgen – als Völkergewohnheitsrecht oder allgemeine ...