The word shall has been a dominant force in legal drafting for a very long time. But no longer.
Strict grammarians insist that, for the English but not the Scots, Irish or Americans, shall is used in the first person to indicate the future tense: ‘I shall go to the dentist by train’. However, it is used in the second and third person to express permission or compulsion: ‘She shall go to the ball‘ and ‘You shall do your homework now‘.
This leaves will to fill in the gaps: ‘We will go’ indicates a determination or decision to go (in the first person); whereas ‘You will go‘ or ‘They will go’ merely indicates the future tense (in the second and third person).
So much for theory. The English are increasingly following the Scottish, Irish and US practice of using ‘I will‘ to indicate the future tense, and using ‘I shall‘ to indicate permission: ‘Shall I speak now? ‘What shall I say?‘
Although shall might once have been thought of as the hallmark of legal drafting, it is increasingly being supplanted by must when an obligation is imposed. This reflects uncertainty over the meaning of shall, as theory and practice diverge.
However, must is not universally accepted, despite its advantage in being unambiguously imperative.
Some argue for a technical distinction: that ‘You must do X‘ refers to an existing obligation imposed elsewhere, whereas ‘You shall do X‘ indicates an obligation being created by the words themselves. This does not seem to be a widely-followed distinction.
Some argue that shall is to be used for stronger obligations than must: sometimes, that must is reserved for requirements attached to optional activities (eg applications must use the prescribed form) whereas shall is for compulsory activities.
By contrast, others find must more forceful than shall. They feel that must has an underlying impertinence: that shall records what a person is required to do, or face the consequences, while must somehow removes the choice of facing consequences rather than complying.
There is a very helpful note by the Office of the Parliamentary Counsel’s Drafting Techniques Group (see here), which has informed much of this piece.
The note concludes that, in the context of legislative drafting, must has the same meaning as shall but ‘is clearer, more modern and more consistent with Plain English drafting. There is no real argument that must is weaker (or stronger) than shall, or that it should be used for directory as opposed to mandatory obligations‘. It concludes that alternatives to shall ought to be preferred when imposing obligations and that must is the clearest and most concise current alternative.
Readers should take note, although I will leave for another day the question whether by that I intend to require or recommend that they do so.