The paper raises a problem of formalising several key concepts in legal theory, namely, goal, function and value. The law is viewed from a perspective of computer science in law. I intend to apply requirements engineering methods in law. The Berman and Hafner's [1993. Representing teleological structure in case based legal reasoning: the missing link. In: Proceedings of the Fourth International Conference on AI and Law. ACM Press, New York, pp. 50–59] challenge to model case-based reasoning in legal domain and the more systematic research, which is collected in Artificial Intelligence and Law journal in 2002, are considered as possible approaches to solutions. The term “goal” covers purposes, policies, interests, values, etc. I find a formalisation to have different levels depending on a distinct meaning of the term “law”. E.g., legal drafting is closer to engineering than to legal reasoning. European Union law and implementation of EU directives provide us with court decisions based on the teleological method. National implementation measures could employ goal-driven systems engineering techniques. Conclusions: (1) the formalisation is a challenging problem, (2) experts from other domains will gain from explicit representation of aims behind the law, (3) analysis of the structure of law is not enough; the studies of the content of law are required, too.