There is a common law defence (known as the "proudman and dayman defence") which can be summarised as having an honest an reasonable belief in a state of FACTS

There is a common law defence (known as the "proudman and dayman defence") which can be summarised as having an honest an reasonable belief in a state of FACTS which, if true, would make the act legal. Note that ignorance of the law is no defence, and dishonest or unreasonable ignorance of the facts is also no defence.