quo warranto= a writ or legal action requiring a person to show by what warrant an office or franchise is held, claimed, or exercised. "rigorous quo warranto proceedings"
'by what authority or warrant'. It is issued by the court to enquire into the legality of the claim of a person to a public office. Hence, it prevents illegal usurpation of public office by a person.
e.g. a person of 62 years has been appointed to fill a public office whereas the retirement age is 60 years. Now, the appropriate High Court has a right to issue a writ of Quo Warranto against the person and declare the office vacant.