Rational choice approaches to customary international law have gained in prominence in recent years. Although becoming increasingly sophisticated, they are not able to explain all phenomena of customary international law. This contribution claims that there are two different types of unwritten...

In their majority, public international lawyers postulate that for a new rule of customary law to originate, two conditions must be fulfilled: there must be consistent practice, and it must be shown that this practice is motivated by the belief that such behaviour is required in law. Maurice...