Overcoming Legal
Defeasibility?
Some authors have suggested that the law ought to be recast into a set
of deductive axioms that would lead to consistent outcomes in any
possible factual situation. This reformulation of the law would
eliminate normative conflicts, and therefore would leave no room for
legal defeasibility. This idea has been affirmed by Alchourrón and
Bulygin (1977): the legislator and the doctrinal jurist should combine
their efforts towards providing axiomatic reformulation of the law, or
at least of particular sections of it. Just as Euclid developed an
axiomatic model of geometry, and as modern natural science and social
science (especially economics) have developed axiomatic models for their
theories, so the legislator and the jurist should axiomatise the law. By
adding to such an axiomatisation a description of a specific case, we
should obtain a set of premises from which the obligations and
entitlements of the parties in the case can be deduced.
Alchourrón (1996) claimed that the ideal of the axiomatization of the
law should inspire legislation and doctrine. It could contribute to
bringing legal studies and scientific method together: just as in
science the phenomena to be explained, the explanandum , should be
the logical consequences of a set of premises, the explanans ,
containing scientific laws and the description of particular facts, so
in law the content of a legal conclusion (the decision) should be the
deductive consequence of a set of premises including both general norms
and the description of specific facts. Systemic interpretation should
have the task of making exceptions explicit, by embedding their negation
into the antecedent of the concerned legal norm (a prima facie norm “if
\(\varphi\) then \(\psi\)” which is subject to exception \(\chi\),
should be rewritten as “if \(\varphi\) and not \(\chi\) then
\(\psi\)”).
It seems to me that even if such a reformulation of the law were
feasible (with regard to all exception that could be identified by the
legal scholar), it is doubtful that it would be useful, i.e., that it
would make the law easier to understand and apply. Legal prescriptions
would need to become much more complex, since every rule would have to
incorporate all its exceptions. In addition, such a representation of
the law would not be able to model the dynamic adjustment that takes
place—without modifying the wording of existing rules—whenever new
information concerning the conflicting rules and the criteria for
working out their conflicts is taken into consideration. Finally, by
rejecting defeasible reasoning, we would forfeit the law’s ability to
provide provisional outcomes while legal inquiry moves on.
The need to represent the law in ways that facilitate defeasible
reasoning does not imply that the current way of expressing legal
regulations in statutes and regulatory instruments cannot be improved.
On the contrary, considerable improvements in legislative technique are
required to cope with the many tasks entrusted to modern legal systems.
However, such improvements should not be aimed at producing a
conflict-free set of legal rules, just for the sake of logical
consistency. They should rather be aimed at producing legal texts that
can more easily be understood and applied. This objective requires
skilful use of the very knowledge structures (such as conceptual
hierarchies, speciality, or the combination of rules and exceptions)
that enable defeasible reasoning.
Accepting defeasibility in the law has significant implications both for
the way we use legal knowledge and for the structure of such knowledge.
On the one hand, deductive inference can be complemented with defeasible
arguments. On the other hand, the acceptance of defeasibility leads us
to viewed the law argumentation basis containing conflicting pieces of
information as well as the criteria for resolving some of these
conflicts. It is important to stress the difference between an
argumentation basis and a deductive axiomatic base. While a deductive
axiomatic base is consistent and flat, an argumentation basis is
conflictive and possibly hierarchical: it includes reasons clashing
against one another, reasons for preferring one reason to other reasons,
and reasons for applying or not applying certain reasons given
particular conditions.
Both strategies just mentioned, namely, representing the law as an
axiomatic base and representing it as an argumentation basis, may be
justified in different contexts. The first strategy may be appropriate
when we want to deepen our analysis of a small set of norms and
anticipate as much as possible all instances of their application,
finding a precise solution for each of them. The second strategy,
however, more directly corresponds to the logical structure of
non-formalized legal language (which expresses the law as setting out
rules and exceptions, principles, preference criteria, etc.), and it
reflects the ways in which legal reasoning proceeds when dealing
conflicting pieces of information: rules and exceptions, different
values needing to be balanced, different norms implementing different
values, competing standards indicating what norms and values ought to
prevail in case of conflict, and so on.
An argumentation basis may be transformed into an axiomatic knowledge
base whose deductive conclusions include all outcomes that would be
defeasibly justified relatively to the given argumentation basis
(assuming that all the facts of the case are known). The dialectical
interaction between reasons for and against certain conclusions, and
between grounds for preferring one argument to another, would be
transformed into a set of conclusive connections between legal
preconditions and legal consequences. Flattening legal information in
this way, however, would entail a loss of information: the deductive
knowledge base would not include a memory of the choices from which it
derives, and therefore it would not contain the information needed to
reconsider such choices—it does not, for example, contain the
information on which it was decided that a certain principle would
outweigh a competing principle or that a certain interpretation was
preferable. To understand the articulation of the relevant legal
reasons, we would need to go back to the original argumentation basis.
Consider, for instance, the domain of privacy. Under EU regulation law
the processing of personal data is admissible only for a specific
purpose that is communicated to the person concerned. Moreover, such
processing is in general admissible only with that person’s consent.
These constraints are justified by the need to protect values such as
individual self-determination and dignity. However, there is a large set
of exceptions to the consent principle, namely, different scenarios in
which data can be processed without consent. These exceptions are
justified by the need to protect the competing rights of others, as well
as certain social values. Moreover, we have cases where consent alone is
insufficient to make data processing permissible, further requirements
being necessary (like the authorization of a data protection authority
for genetic data), and for each such exception specific rationales can
be found that guide interpreters in determining the contents and limits
of the exception. Finally, there may be cases where personal data may be
processed even beyond the explicitly stated legislative scenarios, on
the basis of an authorization which a data protection authority issues
to protect the rights of others, but which overrides the right to
privacy. To determine whether a data protection authority has made
legitimate use of its powers, we need to consider the importance of the
values at stake (privacy, freedom of expression, economic freedom,
health, etc.) and evaluate whether they have been balanced in a way that
respects legal (in particular, constitutional) constraints. We could try
to reduce this multilevel argumentation basis to a set of flat rules,
but what we would obtain is a representation removed from the original
legal texts (laws, regulations, authorizations), and whose contents and
rationales are much more difficult to grasp.