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| Book Title | Customary International Law; A New Theory with Preactical Applications |
| Book Author | Lepard, Brian D. |
| Bibliographic Information | Cambridge University Press, 2010, Pages : 419, $55.00, ISBN 9780521138727 |
| Review Title | |
| Reviewer(s) | Petersen, Niels |
Brian D. Lepard. Customary
International Law. A New Theory with Practical Applications.
Reviewed by Niels
Petersen
The theory of customary international law is one of
the big mysteries of international law scholarship. Every student of
international law knows what customary law is. And yet, nobody knows what it
actually is. Article 38 (1) lit. b of the Statute of the International Court of
Justice defines custom as consistent state practice coupled with an opinio iuris. Although legal scholarship
has filled whole libraries trying to come up with a set of rational criteria to
identify these two elements, there remain many open questions. In his new book
on Customary International Law, Brian
Lepard intends to advance legal scholarship in the search for answers. He
promises to “develop a new theory of customary international law that […] helps
to solve its theoretical and practical puzzles” (pp. 11-12).
The core of Lepard’s theory is the reduction of the
two constitutive elements of customary law to one – opinio iuris: a “customary international law norm arises when
states generally believe that it is desirable now or in the near future to have
an authoritative legal principle or rule prescribing, permitting, or
prohibiting certain conduct.” (pp. 8, 97-98). State practice is not perceived
as a mandatory requirement, but merely as evidence of this belief (p. 98). With
this focus on opinio iuris, Lepard
follows a popular trend among international law scholars. There have been
several recent attempts to diminish the importance of state practice for the
identification of unwritten international norms.[1] The
rationale behind this tendency is the strengthening of norms with moral impact,
such as international human rights law, as we often observe a divergence
between official declarations of states and the actual practice in this area.
For the identification of an opinio iuris, Lepard makes two presumptions. The first presumption
is inspired by game theory: whether states view a norm as authoritative depends
on the structure of the social dilemma. If states face a harmony game, in which
all states have unconditional incentives to cooperate, or an assurance game, in
which cooperation yields the best individual outcome if all other states
cooperate as well, legal norms are not necessary to produce the best social
outcome – the social process will produce the best outcome anyway. Therefore,
Lepard argues that there is a presumption that states do not desire an
authoritative norm (p. 103). If we have a coordination problem, in which
cooperation equally yields the highest individual pay-offs, but which have
multiple equilibria, Lepard presumes
the desire to establish an authoritative norm. In a prisoner’s dilemma
situation, finally, states have incentives to defect from the socially optimal
solution. Therefore, the author argues that there should be an even stronger
presumption that states want to establish an authoritative norm.
However, these propositions concern only the amount of
evidence necessary for identifying opinio
iuris. With regard to the level of consensus necessary for the
establishment of a customary norm, the situation is different. Here, Lepard
requires the highest level of consensus in a prisoner’s dilemma situation
because conflict is most likely in such situations (p. 159). In contrast,
coordination problems demand a lower level of consensus, and, if the structure
of the social dilemma is an assurance game, a “small” majority shall already be
sufficient (p. 158).
The second presumption concerns the ethical framework
of Lepard’s theory. If certain norms objectively further fundamental ethical
principles, we should presume that these norms have legal authority (pp.
110-111, 140). Where do these fundamental ethical principles come from? Lepard
establishes a preeminent ethical principle, which he calls “unity in diversity”
(p. 78). According to this principle, all individuals are members of one human
family, who morally ought to be united, while recognizing that differences in
race, religion, nationality enrich this single human family. Lepard claims that
this principle has been explicitly endorsed by states in international treaties
and declarations.
From this preeminent ethical principle, Lepard derives
further ethical principles: essential ethical principles, compelling ethical
principles and fundamental ethical principles, which differ in how closely they
are “logically” related to the principle of unity in diversity (pp. 81-82). These
ethical principles comprise certain human rights, such as the right to life,
the right to subsistence and the right to freedom of moral choice, the respect
for state autonomy, the punishment of criminals, the principle of open-minded
consultation and the duty to honor treaties (pp. 82-92).
The presumptions established by Lepard are rebuttable.
They are means for setting standards with regard to the required weight of the
evidence for an opinio iuris. They
are not supposed to substitute for the latter. Nevertheless, both presumptions
are questionable. Lepard requires, at the same time, the least evidence and the
highest level of consensus for opinio
iuris in situations where conflict is most likely – when states face a
prisoner’s dilemma situation. However, the prisoner’s dilemma seems to be
exactly the situation where deviating from the consensus requirement seems to
be worthy of some consideration.
Let us consider an example. Climate change is often
perceived to be a model case of a multilateral prisoner’s dilemma. The
polluting state reaps the benefits of its polluting conduct, while the costs
are borne by all members of the international community. However, costs and
benefits are not distributed in the same way. Industrialized states draw more
benefits from polluting than developing countries, while certain states are
more affected by global warming than others. The interests of states with
regard to the best solution may therefore diverge significantly, so that some
states might rationally oppose the formation of a global norm.
Does this mean that we should respect the autonomy of
a state opposing the norm? Not necessarily. Let us assume that we have a highly
industrialized state A, whose industrial emissions contribute significantly to
the increase of global warming. Global warming leads to a rise in the sea
level, which might endanger the existence of island state B. Imposing emission
standards would now certainly interfere with A’s autonomy, but not imposing them would affect B’s
autonomy probably to an even greater extent. Requiring a high level of
consensus because a certain solution might not be the “preferred outcome of any state” (p. 159) thus does not give
sufficient consideration to the complexity of the matter. The question is not
whether the autonomy of a certain state is restricted, but rather how we
resolve the conflict of competing autonomies.
The question of which
standard to impose is, of course, a difficult one. Even if we agree that the
reduction of pollution is socially desirable, we still do not know much about
the standards. By how much should emissions be reduced? Are there different
obligations for industrialized nations than there are for developing countries?
Lepard does not address these difficulties by requiring only a minimal amount
of opinio iuris in such
constellations. Unfortunately, he does not explain how this works in hard cases
in practice.
With regard to his ethical framework, Lepard derives
his preeminent ethical principle of unity in diversity from the text of
international declarations and treaties. However, even if we observe that
states indeed recognize the principle of unity and diversity, the texts do not
reveal that this principle should be the centerpiece of the moral framework of
customary international law, and that it should be used as a guiding principle
in interpreting and evaluating evidence for an opinio iuris. How do we know that? Lepard does not give any
analytical reasons. Instead he refers to “the world’s most prominent ethical
thinkers”, such as Immanuel Kant, John Stuart Mill or Peter Singer
(p. 79), and “the sacred texts of the great religions of the word” (p.
80). A more thorough analysis of why the principle of unity and diversity
should have such a preeminent role would have made his point more convincing.
Lepard then claims that the other fundamental ethical
principles he identifies “logically flow” from the preeminent principle (p.
81). However, the effort to establish a link between the fundamental principles
he lists and the preeminent principle of unity in diversity is not always
convincing. His reasoning is often apodictic. What we find are citations of
international documents mentioning these principles. What we search for in
vain, however, are reasons for why they are logically
related to the preeminent principle.
After having laid out his general theory, Lepard
continues to discuss the main topics that you would expect in a book on
customary international law in the light of his theory. He analyzes the amount
of consensus necessary for the formation of customary law, the relationship of
custom to general principles of law (article 38 (1) lit. c ICJ Statute), the
sources of evidence for opinio iuris,
such as treaties and General Assembly resolutions, the role of persistent
objectors as well as the status of jus
cogens norms and norms erga omnes.
In the last part of his book, he finally applies his
theory to four examples, of which three emanate from the field of human rights,
where his moral framework probably has the biggest impact. The one example that
does not originate in the field of human rights is the discussion on whether
the arms length standard in international tax law can be considered to be a
customary norm. Lepard answers the question in the negative, as agreements
introducing the standard are only bilateral and thus not generalizable.
Furthermore, the arms-length standard does not directly realize fundamental
ethical principles so that there is no presumption in favor of a customary norm
(p. 300). The most interesting analysis in the field of human rights is
his argument that there is a customary right to change one’s religious beliefs.
Lepard cites several international documents supporting such a right (pp.
348-59), points out the proximity to the principle of unity in diversity (p. 360),
and even cites Qur’anic verses emphasizing the freedom of religion in support
of his argument (p. 363).
At large, Lepard has developed an original theory of
customary international law. It remains to be seen, however, whether his theory
will really have an impact on the solution of the theoretical and practical
puzzles of the field. His conception leaves too many questions unanswered.
Although he tries to avoid a profuse natural law flavor of his ethical
framework by linking it to international documents and the philosophical and
religious discourse, the basis of the framework is still nebulous. Concerning
the structural analysis of social dilemmata, it is a benefit of Lepard’s
analysis that he realizes that the question of customary law does not deserve a
one-size-fits-all approach. Different incentive structures may require
different solutions. However, the concrete analysis of this problem leaves a
lot to be desired. Lepard’s book is certainly a contribution to the discussion.
However, international law scholarship has still some way to go to solve the
mystery of customary law.
[1] See, e.g., B. Cheng, ‘United Nations Resolutions on Outer Space: “Instant”
International Customary Law?’, 5 Indian J. Int’l L. (1965) 23; B. Simma
and P. Alston, ‘The Sources of Human Rights Law: Custom, Jus Cogens, and
General Principles’, 12 Austl. Yb. Int’l L. (1992) 82; J. Tasioulas, ‘In
Defence of Relative Normativity: Communitarian Values and the
