Black's Law Dictionary (2nd edition)dictionaries

Functus Officio

Lat. Having ful-fllled the function, discharged the ofiice, or accomplished the purpose, and therefore of no further force or authority. Applied to an officer whose term lias expired, and who has consequently no further official authority; and also to an instrument, power, agency, etc., which has fulfilled the purpose of Its creation, and is therefore of no further vlr-tue or effect

Source: Black’s Law Dictionary 2nd Ed (1910)