Specification Languages for Computational Laws Versus Basic Legal Principles

ABSTRACT We speak of computational law when it is intended to be enforced by software through an automated decision-making process. As digital technologies evolve to offer more solutions for public administrations, we see an ever-increasing number of computational laws. Traditionally, law is written in natural language. Computational laws, however, suffer various complications when written in natural language, such as underspecification and ambiguity, which lead to a diversity of possible interpretations by the coder. These could potentially result into an uneven application of the law. Thus, resorting to formal languages to write computational laws is tempting. However, writing laws in a formal language leads to further complications, for example, incomprehensibility for non-experts, lack of explicit motivation of the decisions, or difficulties in retrieving the data leading to the outcome. In this paper, we investigate how certain legal principles fare in both scenarios: computational law written in natural language and written in formal language. We use a running example from the European Union ‘s road transport regulation to showcase the tensions arising, and the benefits from each language.

KEYWORDS Law - Computational law - Legal principles - Information technologies - Specifications

TABLE OF CONTENTS 1. Introduction. – 1.1.Plan of the paper. – 1.2. On road transport. – 1.3. This paper compared to existing literature. – 2. Some legal principles at stake. – 2.1. Legality. – 2.2. Legal Certainty. – 2.3. Prohibition of Arbitrariness. – 2.4. Motivation. – 2.5. Clarity. – 2.6. On the choice of these principles. – 3. Natural vs. formal languages. – 3.1. A natural language specification of Art. 6.1. – 3.2. On formal language specifications. – 3.3. A formal language specification of Art. 6.1. – 3.4. Natural vs. formal specification languages. – 4. Natural language issues. – 4.1. Particularities of Art. 6.1. in natural language. – 4.2. Legal principles in natural language law. – 4.2.1. Legality. – 4.2.2. Legal Certainty. – 4.2.3. Prohibition of Arbitrariness. – 4.2.4. Motivation. – 4.2.5. Clarity. – 5. Formal-language issues. – 5.1. Formal verification. – 5.2. Legal principles in formal-language law. – 5.2.1. Legality. – 5.2.2. Legal Certainty. – 5.2.3. Prohibition of Arbitrariness. – 5.2.4. Motivation. – 5.2.5. Clarity. – 6. Conclusions