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.