Hierarchy of sources
[T]he system of international law consists of erratic parts and elements
which are differently structured so that one can hardly speak of a ho-
mogeneous nature of international law. This system is full of universal,
regional or even bilateral systems, subsystems and sub-subsystems of
different levels of legal integration.1
We start this chapter with a description of some of the features of the sources of international law that may complicate an examination of conflict of norms in public international law. We then ask whether there are any a priori hierarchies in international law and, thereafter, examine the principal sources of international law as they may play out in a conflict of norms. We conclude the chapter by redefining international law as constituted by, first, general international law and, second, particular international law.
It is generally recognised that norms of international law may derive from the following five sources: treaties; custom; general principles of law; unilateral acts of states; and acts of international organisations. Obviously, a distinction must be made between these five ‘sources’ of law and the infinite number of ‘norms’ they may produce.
The first three of these sources – treaties, customary law and general principles of law – are explicitly confirmed in Art. 38(1)(a)-(c) of the
1 Gerhard Hafner, ‘Risk Ensuing from Fragmentation of International Law’, ILC, Report on the Work of its 52nd Session, General Assembly, Official Records, 55th Session, Supplement No. 10 (A/55/10), 321.