1) UK: A member of the British army that knows every paragraph, clause and sub clause of the Kings or Queens regulations, a book regulating discipline in the British forces.
2) A person that can get out of trouble by a thourogh knowlege of the rules.
1: Private Houdini's been charged with insubordination, do you think he will be found guilty?
2: Nah! He will get away with it again by quoting Queens regulations, he is a true barrack room lawyer.