from
Bouvier's Law Dictionary, Revised 6th Ed (1856)
MAY To be permitted; to be at liberty; to have the power.
2. Whenever a statute directs the doing of a thing for the sake of
justice or the public good, the word may is the same as shall. For example,
the 23 H. VI. says, the sheriff may take bail, that is construed he shall,
for he is compellable to do so. Carth. 293 Salk. 609; Skin. 370.
3. The words shall and may in general acts of the legislature or in
private constitutions, are to be construed imperatively; 3. Atk. 166; but
the construction of those words in a deed depends on circumstances. 3 Atk.
282. See 1 Vern. 152, case. 142 9 Porter, R. 390.