Logic and legislation

The basics of symbolic formal logic as a useful tool for legislative counsel

I have written a guide to basic symbolic logic for legislative drafters in the Loophole – the journal of the Commonwealth Association of Legislative Counsel, 2021 issue 2, October.

This issue of the Loophole is a large file, and there were some formatting improvements I could make to my article, so here is a reformatted extracted version of the article –

logic-for-legislative-drafters-loophole-2021-02Download

I am hoping it will help legislative drafters apply the tools of logic to our drafts, to help check for logical inconsistencies but also to prompt us to take more care over two aspects in particular.

One is whether we are sure that it is clear, when we write “if this and that, a person must do the other”, what is meant to happen for “if not this and that”. The basic answer is that the person is not obliged by this provision to do the other. But do we sometimes mean no other provision of this draft is going to oblige the person to do it, or sometimes even that no other legal obligation outside of this draft is going to stand? This approach fits also with the computer logic “if, else” pattern, where most imperative programming languages expect the programmer to specify what happens if the condition is not met. It is a separate question from “defeasibility” – whether there is something else lurking in this draft, or elsewhere in other statutory/common law, that creates an exception where even though the condition holds the obligation in fact does not apply.

The other aspect is a development from what happened when most drafting offices started replacing “shall” with “must” – we found “must” does not always fit. That has made us more aware of the differences between –

• the classic “must” as an imposition of a sanction-backed obligation on a person,
• the thinner “must”, such as “an appeal must be lodged within 4 weeks of the decision” – where there is no obligation to lodge the appeal in the first place, and the only sanction for late lodging is that the appeal does not count as made and does not spark any duties of the appellate body,
• the operation of law cases – “there shall be established a body corporate called the Regulator of Statutes” becomes “there is a body corporate called the Regulator of Statutes”, not “there must be established a body corporate called the Regulator of Statutes”, and
• the definitional/constitutive cases – ” ‘Regulator of Statutes’ shall mean the body established by section 2″ becomes ” ‘Regulator of Statutes’ means the body established by section 2″, not ” ‘Regulator of Statutes’ must mean the body established by section 2″.

I hope this will help to improve the rigour we already seek to impose when we are using common sense logic to check our drafts. But it might also help us understand what computer programmers and others are doing with “Rules as Code” and other forms of computational law. The article may also be useful in helping those other people to understand how legislative drafters structure modern drafts and what background law & conventions are operating.