When may means must: deontic modality in English statute construction

Abstract

As well as rules which forbid certain actions or impose certain duties, all modern legal systems include power-conferring rules, which grant rights without imposing norms of behaviour. The distinction between obligations and rights is commonly expressed in statutory language, as in ordinary speech, through the use of modal verbs. In English statutes, shall is normally used to impose an obligation, while may is generally used to confer a discretionary or enabling power. This use is illustrated uncontroversially, for example in “A local authority may within their district [...] construct a public sewer [...].” (Public Health Act 1936 s15[1]) [my emphasis]1 The modal verb is here seen as conferring a right, rather than as imposing an obligation. The question occasionally arises as to whether in particular circumstances the holder of the power, in this case the local authority, could be legally obliged to act under the relevant statute, and if so whether and in what sense enabling expressions like may could then be said to impose a duty. Various courts have held that in certain circumstances there may indeed be an obligation to exercise a statutory discretion. In such cases, the statutory may is said to have a coercive meaning similar to must. Surprisingly, this is the first sense given under ‘may’ in Stroud’s Judicial Dictionary (Stroud: 1986). This reference book gives as synonyms various other legal expressions normally used to grant a discretionary power, including ‘it shall be lawful’, and ‘shall hereby have power’. Where shall occurs in such contexts, it does not have the effect of creating a new legal obligation or duty, but functions as part of an enabling expression to create a new legal power. Linguists commonly accept that expressions literally signifying permi ssion can be used to imply an obligation. However, they would be reluctant to accept the more radical claim implicit in the relevant judgments, that, under certain conditions, may can be understood, in its literal meaning, as including not just a permissive but also a coercive sense. This conclusion is reached through different forms of legal analysis, illustrated here in Julius 1880, Re Shuter (2) 1959 and Anns 1977.