barrack-room lawyer

noun

1. a person who freely offers opinions, esp in legal matters, that he or she is unqualified to give

Example Sentences

It might have helped had he possessed a natural leader in the manner of Newastle's their former captain Nolan but the midfielder was offloaded two summers ago when the St James' Park hierarchy decided against offering a lucrative new contract to a man sometimes perceived as a barrack-room lawyer.

From The Guardian

At Aldershot one of his most popular pieces as an entertainer is that in which he impersonates the barrack-room lawyer.

From Project Gutenberg