Sarah Lawsky (Northwestern) presents A Logic for Statutes, 21 Fla. Tax Rev. ___ (2018), Formalizing the Code, 70 Tax L. Rev. 377 (2017), at Florida today as part of its Graduate Tax Speaker Series:
A Logic for Statutes:
Case-based reasoning is, without question, a puzzle. When students are taught to “think like lawyers” in their first year of law school, they are taught case-based common-law reasoning. Books on legal reasoning are devoted almost entirely to the topic. How do courts reason from one case to the next? Is case-based reasoning reasoning from analogy? How should case-based reasoning be modeled? How can it be justified?
In contrast, rule-based legal reasoning (as exemplified in much statutory reasoning) is taken as simple in legal scholarship. Statutory interpretation — how to determine the meaning of words in a statute, the relevance of the lawmakers’ intent, and so forth — is much discussed, but there is little treatment of the structure of statutory reasoning once the meaning of the words is established. Once the meaning of terms is established, statutory reasoning is considered, roughly speaking, to be deductive reasoning.
This essay examines the structure of statutory reasoning after ambiguities are resolved and the meaning of the statute’s terms established. It argues that standard formal logic is not the best approach for representing statutory rule-based reasoning. Rather, the essay argues, using the Internal Revenue Code and accompanying regulations, judicial decisions, and rulings as its primary example, that at least some statutory reasoning is best characterized as defeasible reasoning — reasoning that may result in conclusions that can be defeated by subsequent information — and is best represented using default logic. The essay then addresses the practical and theoretical benefits of this alternative understanding of rule-based legal reasoning.
Formalizing the Code:
The Internal Revenue Code is notoriously complex, both substantively and structurally. This article examines one source of structural complexity in the Internal Revenue Code: dependency among sections that stems from defined terms. In particular, the article examines what it terms the problem of “definitional scope”: when the structure of the Code leaves unclear to what a term refers. The article uses the problem of definitional scope as a case study to suggest that those who draft tax legislation should formalize proposed statutory language — translate it into logical terms — prior to its enactment.
Formalization could help drafters avoid unintentional ambiguity and refine the language used in the statute; it could provide helpful guidance for those wishing to interpret the statute; and, most importantly, it could help move the law closer to legibility by a computer — that is, it could help on the journey to actual legal artificial intelligence.