(Latin for "from a dishonorable cause an action does not arise") is a legal doctrine which states that a plaintiff will be unable to pursue legal remedy if it arises in connection with his own illegal act. Particularly relevant in the law of contract, tort and trusts, is also known as the "illegality defence", since a defendant may plead that even though, for instance, he broke a contract, conducted himself negligently or broke an equitable duty, nevertheless a claimant by reason of his own illegality cannot sue.