Latin, a legal maxim meaning “the expression of one thing is to exclude another.” The legal concept is that if the legislature mentions specifically mentions only certain items from a larger class of items, it meant to include only the items specified and to exclude those items that were omitted.
“An implied exclusion argument lies whenever there is reason to believe that if the legislature had meant to include a particular thing within the ambit of its legislation, it would have referred to that thing expressly. Because of this expectation, the legislature’s failure to mention the thing becomes grounds for inferring that it was deliberately excluded. Although there is no express exclusion, exclusion is implied.” Ruth Sullivan, Sullivan and Driedger on the Construction of Statutes, 4th ed. (Markham: Butterworths, 2002) at 186-187.