HOW IS CUSTOMARY INTERNATIONAL LAW CHANGED?

In light of the previous analysis, it is possible to draw certain conclusions about how new norms of customary international law are created and how existing norms are terminated. This process has long been a matter of some mystery.

In general, as the proposed definition of customary international law suggests, new customary norms come into existence when states generally believe that it is desirable now or in the near future to implement them as authoritative legal norms. State practice may be strong evidence of this new belief, but it is not essential. Thus, states do not have to engage in practice inconsistent with an existing norm in order to change it.

Some commentators who believe that state practice is an essential independent requirement of customary law have maintained just this – that a new norm of customary law that conflicts with an existing one can only be created by new practice that violates the existing norm. These scholars and others may also believe that a new opinio juris cannot precede new state practice because opinio juris is acceptance of a preexisting practice.

Under the theory proposed here, changed state practice is not necessary, nor does it need to precede opinio juris. Accordingly, a rule does not have to be changed through a violation.