have stressed and stretched two distinct but related areas of international law: the right of self-defence, and the rules of international humanitarian law. I conclude by arguing that even a disproportionately powerful state is constrained, in its ability to change international law, by the actions of other countries and public opinion – both at home and abroad.
There are two principal sourcesofinternationallaw. ‘Customary international law’ is an informal, unwritten body of rules deriving from a combination of ‘state practice’ and opinio juris . State
considered as possible additional sources or lawmaking processes, however, for the purpose of this contribution we will not evaluate the nature of protests as a separate independent source, but rather their role in customary lawmaking. See e.g. A Cassese , International Law (2nd edn, Oxford University Press 2005 ) 184 ; H Thirlway , ‘ The SourcesofInternationalLaw ’ in MD Evans , International Law (3rd edn, Oxford University Press 2010 ).
81 MH Mendelson , The Formation of Customary International Law (Recueil des cours 272, Martinus
implicit for strategic reasons. Yet one implicit
hint at basic differences concerns the question of what sourceofinternationallaw either discourse privileges, with sovereigntists emphasizing treaty law and
interventionists stressing customary law. Though both types of law in practice
complement each other and are interwoven, theoretically, they are based on
different ideas of how international law emerges: treaty law rests upon explicit
state consent, whereas customary law refers to the collectivity of states and is
almost unaffected by the disapproval of a single
prevailing among civilized
peoples, by the laws of humanity, and by the demands of
Some authorities hold that a consequence of the Martens
Clause was to add the said ‘laws of humanity’ to the
recognized sourcesofinternationallaw. Antonio Cassese has
challenged this understanding of its significance, however.
The clause was formulated, he argues, as a diplomatic move
to break a deadlock at the 1899 Hague Peace Conference,
and it cannot be treated as having raised either the laws of
humanity or the dictates of public conscience to the status of
the one hand, Kennedy’s argument about how the legacy of Christianity
was generally seen as peaceful, moderating the calamities of and even
preventing war, would not – as a historical claim – have disturbed later
scholars. Interpreting all other sourcesofinternationallaw as having
been influenced and positively furthered by Christianity – for example,
Roman law, the spread of commerce, the general progress of civilisation – was an assumption that, although often implicit, seemed to stick. 30
On the other hand, later scholars would have distanced themselves from
, ‘Recommendations and the Traditional SourcesofInternationalLaw’ (1997) 20 German Yearbook of International Law 103 at 118.
43 Article 25 UN Charter 1945.
44 Ibid. Articles 41 and 42.
45 Ibid. Articles 36(1) and 39.
46 Articles 36 and 65 ICJ Statute 1945.
47 Crawford (2014) n. 9 at 461.
48 W.B. Gwynn, The Meaning of the Separation of Powers (Nijhoff 1965) 1.
49 Ibid. 101.
50 Articles 60, 63, 64 UN Charter 1945.
51 T.M. Franck, ‘The Bona Fides of Power: The Security Council and Threats to the Peace’ (1993) 240 Hague Recueil 190.
during his lifetime, and translated into French and English. 68 Fiore, whose work anticipated the international
law of human rights, 69 was of the view
that the ultimate sourceofinternationallaw was the juridical conscience of
European peoples. 70 Human society was
‘universal’ but only fully civilized states could be members of what
he called the Magna civitas , the juridical community. He had doubts whether
civilization could extend uniformly to all parts of the
traditional view on how norms in international law, including customary rules, are generated. McCorquodale, for instance, opines that
to consider only state practice and state opinions … to determine customary international law as a ‘source’ ofinternationallaw is a fiction created by the dominant legal doctrine … In an international legal system where non-state actors are participants, the practice of these actors, their role in the creation, development and enforcement of law and their actions within the international and national communities … can, and should, be
the external relations of the Organisation with States, on the other.
The contribution of legal opinions of the Secretariat to the formation of rules of customary international law lies in part in their influence in shaping and orienting the conduct of the Secretary-General, the Secretariat, and other United Nations organs. The role of the legal opinions that are prepared by the Office of Legal Affairs 60 and generally attributed to the Legal Counsel (and sometimes to the Secretary-General himself) is particularly related to custom as a sourceofinternational
generations from the scourge of war
to reaffirm faith in fundamental human rights, in the dignity and worth of the human person, in the equal rights of men and women and of nations large and small
to establish conditions under which justice and respect for the obligations arising from treaties and other sourcesofinternationallaw can be maintained
to promote social progress and better standards of life in larger freedom.
The Charter was signed in San Francisco in June 1945 by fifty states. The signatories promised to be bound