Civil offence was a term of art in military law in the United Kingdom.
In the Army Act 1955 (3 & 4 Eliz. 2. c. 18) and the Air Force Act 1955 (3 & 4 Eliz. 2. c. 19), the expression "civil offence" meant any act or omission punishable by the law of England or which, if committed in England, would be punishable by that law.[1] [2]
As to this definition, see Cox v Army Council [1963] AC 48, HL.
Section 42(1) of the Naval Discipline Act 1957 (5 & 6 Eliz. 2. c. 53) defined a civil offence as "any act or omission which is punishable by the law of England or would be so punishable if committed in England."[3]
See now the offence of "criminal conduct" under section 42 of the Armed Forces Act 2006.
It is a misnomer to describe a civil wrong as a "civil offence".[4]