What does the legal rule expressio unius est exclusio alterius mean in statutory interpretation?

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President Lyndon B. Johnson signs the Medicare Bill at a table beside former President Harry S. Truman, with Lady Bird Johnson and others standing behind them. — Legislation Former U.S. president Harry S. Truman (right) looking on as U.S. Pres. Lyndon B. Johnson signs the Medicare bill at the Harry S. Truman Library and Museum in Independence, Missouri, July 30, 1965.

In the context of statutory interpretation, the legal canon expressio unius est exclusio alterius is a rule of construction used by courts to determine the intent of the legislature.1

The phrase translates to "the expression of one thing is the exclusion of the other." In practice, this means that when a statute explicitly lists specific circumstances, persons, or items to which it applies, that enumeration indicates an intention to exclude all other circumstances, persons, or items that were not mentioned.1

This rule serves as an intrinsic guide, helping judges interpret the scope of a law by assuming that the legislative body intentionally omitted what it did not include in its list.1