Der Wandel des ungeschriebenen Völkerrechts im Zuge der Konstitutionalisierung

The role of state practice in the formation of unwritten international law has attracted a lot of attention in recent decades. According to the traditional view, state practice is one of the two constituent elements of customary international law. In practice, its importance is however decreasing. Modern international law scholarship increasingly turns to interpretative methods when identifying customary law. In this process, international courts and tribunals as well as international law scholars only pay lip service to state practice. This contribution analyzes this development and proposes to distinguish two types of unwritten norms. On the one hand, there is customary law, which still requires the evidence of state practice as a constituent element. On the other hand, however, there are general principles. These general principles can be identified by the mere recurrence to opinion iuris. The distinction between both types of norms is based on a classification drawn from legal theory. This classification distinguishes conduct-related rules from interest-related principles. While the former are to be seen as customary norms in the traditional sense, the latter may be qualified as general principles. In the final section, this proposal is related to the discussion on the constitutionalization of international law. It is argued that the emergence of legal principles is a necessary step in international law's development to a modern legal order.