Customary law has been criticized from very different angles. Rational choice theorists claim that what looks like custom is nothing but self-interest. Positivists doubt that anything beyond consent assumes the force of law. In this paper, we adopt an experimental approach to test these claims....

The novel part of this paper is a model of the principle of proportionality, as the cornerstone of the doctrine of fundamental rights. German law, and with some modifications also the law of the European Community and the European Convention on Human Rights, do not categorically outlaw...