Rules lawyer Rules lawyer Tossa de Mar Category="Role-playing game terminology"Category="Slang"Rules lawyer is a derogatory Slang expression. In role-playing games such as Dungeons & Dragons, a rules lawyer is a Player who knows, or thinks he knows, even the most arcane and technical rules. A rules lawyer may attempt to use his supposedly-encyclopedic knowledge of the rules to gain unfair advantage, to ingratiate himself with other players, or simply to annoy the Game Master.