Letters of fire and sword were a Scottish legal instrument.
If a criminal resisted the law and refused to answer his citation, it was considered treason in the Scottish courts; and “letters of fire and sword” were sent to the sheriff, authorising him to use either or both these instruments to apprehend the contumacious party.
[1] Letters of Fire and Sword were issued against the following clans: This article incorporates text from a publication now in the public domain: Brewer's Dictionary of Phrase and Fable 1898 edition page 464 entry Fire and Sword