Nora and Seth Tillman have published this fragment on the constitutional meaning of “shall” and “may.” They contend that in 18th Century America the word “shall” was used more often in a non-obligatory sense, ie, to indicate futurity as we would use the word “will,” than it would be today. This may be important in construing certain constitutional provisions where the use of “shall” is arguably non-mandatory.
For example, the Appointments Clause provides that the President “shall” nominate and appoint Ambassadors, Ministers and Consuls, Supreme Court Justices, and all other officers of the United States. The word “shall” in this sentence could be mandatory (must), directory (should) or permissive (may). The Tillmans argue that we should not be too quick to assume that the word was used in the mandatory sense, as 18th century usage would be more consistent than current usage with the directory or permissive senses (though it seems to me unlikely that the framers would have used “shall” rather than “may” had they intended the Clause to be permissive).