How have the courts dealt with the issue of ambiguity in the use of the word "may not"?

As for the alleged ambiguity in the use of the words “may not” the panel has dealt with such an argument in Shah v. Canada.[3] For the same reason expressed therein the panel must reject any suggestion that the use of the words “may not” is ambiguous. Used by itself the word “may” is permissive. It implies that a person may do something and conversely it implies that they “may not” do something. Used in combination with “not” the phrase loses its permissive character and assumes that of a prohibition or a negation. In the same sense as the word “shall” implies a requirement or something that is mandatory and the words “shall not” implies an absolute prohibition when the words “may not” are used in the context of statues, regulations and documents it means that something is not possible, prohibited; in this case future sponsorship.

While the appellant did not speak English at the time, she apparently was able to inform herself as to the contents of the declaration sufficiently to form the opinion that its interpretation admitted of ambiguity. This is unfortunate but not something to upset the effect of the declaration. As the respondent correctly observed, this panel has upset the fact of a declaration in the past in Chen v. Canada [4] but it did so on the basis of irregularities in its production and not on the basis of ambiguity in the way its wording was interpreted, that is for procedural and not substantive reasons.